Glossary

Search marketing glossary

Plain-English definitions of 95 terms across SEO, PPC, Digital PR, link building and AI search, each checked against its sources.

Reviewed by Gareth Hoyle, Managing Director
Last reviewed 31 October 2026

Search marketing has its own vocabulary, and AI search has added a new layer to it. This glossary defines the terms we use every day across SEO, PPC, Digital PR, link building and generative engine optimisation, in plain English, with the sources behind each fact. Every definition links to a fuller explanation and to the service it belongs to.

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GEO and AI search

AI citations

AI citations are the links and source references that AI assistants attach to their answers to show where information came from. ChatGPT, Perplexity, Google AI Overviews and AI Mode all cite web pages, and a cited page can earn visibility and clicks without ranking in Google's top 10.

AI hallucination

AI hallucination is when an AI assistant like ChatGPT or Gemini states something false or invented as if it were fact, for example a wrong price, a made-up statistic or a source that does not exist. OpenAI defines hallucinations as plausible but false statements generated by language models.

AI Overviews

AI Overviews are AI-generated summaries that Google shows at the top of some search results pages. They answer the query in a few paragraphs or a list and link to the web pages used as sources, so a page can be cited without ranking first.

AI share of voice is the proportion of AI-generated answers in a category that mention a brand, measured against competitors across a fixed set of prompts. It shows how often ChatGPT, Gemini, Perplexity or Google's AI features recommend a brand compared with its rivals.

Answer engine optimisation (AEO)

Answer engine optimisation (AEO) is the practice of structuring content so that search engines, voice assistants and AI chatbots can lift a direct answer from it. The term is most associated with featured snippets and voice search, and now overlaps heavily with generative engine optimisation.

Entity SEO

Entity SEO is the practice of helping search engines and AI systems recognise a brand, person, product or place as a distinct thing with known attributes, rather than as a string of keywords. It relies on consistent facts, structured data and links between trusted sources.

Generative engine optimisation (GEO)

Generative engine optimisation (GEO) is the practice of shaping a brand's content and wider web presence so that AI systems such as ChatGPT, Perplexity, Gemini and Google AI Overviews mention it, cite it and describe it accurately when they generate answers to users' questions.

Google AI Mode

Google AI Mode is a conversational search mode in Google Search that answers complex, multi-part questions with an AI-generated response and links. It runs many related searches behind each question, supports follow-up questions and appears as its own tab on the results page.

Knowledge graph

Knowledge graphs are databases that store real-world entities, such as people, companies, places and products, with facts about them and the relationships between them. Google's Knowledge Graph, launched in 2012, held over 500 billion facts about five billion entities by 2020 and supplies the facts in knowledge panels.

Large language model (LLM)

Large language models (LLMs) are AI systems trained on huge amounts of text to predict the next word in a sequence. That one skill lets them answer questions, summarise documents and write. ChatGPT, Gemini, Claude and the answers in Perplexity are all generated by LLMs.

LLM visibility

LLM visibility is how often, how prominently and how accurately a brand appears in answers from large language model tools such as ChatGPT, Claude, Gemini and Perplexity. It covers mentions, citations, recommendations and the facts an assistant states about the brand.

llms.txt

llms.txt is a proposed standard for a Markdown file placed at a website's root (/llms.txt) that gives large language models a short summary of the site and a curated list of links to its most useful pages, ideally with clean Markdown versions of each.

Perplexity

Perplexity is an AI answer engine that searches the web in real time and writes a direct answer to a question, with numbered footnotes linking to the sources it used. It runs its own search index and crawler, PerplexityBot, so visibility in Perplexity depends on being crawled and retrieved by it.

Prompt tracking

Prompt tracking is the regular monitoring of how AI assistants answer a fixed set of prompts relevant to a business, recording whether its brand is mentioned, cited and described correctly. It is the AI search equivalent of rank tracking, but measures frequency across repeated runs rather than one position.

Query fan-out

Query fan-out is the technique AI search systems use to split one question into several related sub-queries, run those searches in parallel and combine the results into a single answer. Google says AI Mode and AI Overviews may use it, and other AI assistants retrieve pages in a similar way.

Retrieval-augmented generation (RAG)

Retrieval-augmented generation (RAG) is a method where an AI system first retrieves relevant documents, such as web pages, and passes them to a language model that writes the answer from them. It is the approach behind AI search tools such as ChatGPT search and Perplexity, which ground answers in current pages and cite them.

Semantic search

Semantic search is search that matches the meaning of a query rather than its exact words. It usually works by turning queries and documents into embeddings, lists of numbers that place similar meanings close together, so a page can be found for a question it never phrases the same way.

Structured data for AI search

Structured data for AI search is machine-readable code, usually schema.org vocabulary in JSON-LD, that states the facts on a page explicitly: what the page is about, who published it, prices, dates, authors and products. It helps search engines and AI systems interpret content without guessing.

SEO

301 redirect

A 301 redirect is an HTTP response, 301 Moved Permanently, that tells browsers and search engines a page has moved to a new URL for good. Google treats it as a strong signal that the new URL should be the canonical one, and the redirect passes ranking signals such as PageRank to it.

Canonical tag

A canonical tag is a link element, rel="canonical", placed in the head of a page to tell search engines which URL is the preferred version when the same or very similar content is available at several URLs. Google treats it as a strong signal rather than a command, and can choose a different canonical.

Core Web Vitals (CWV)

Core Web Vitals are three Google metrics that measure real users' experience of a web page: Largest Contentful Paint (LCP) for loading, Interaction to Next Paint (INP) for responsiveness and Cumulative Layout Shift (CLS) for visual stability. Each is assessed at the 75th percentile of page visits.

Crawl budget

Crawl budget is the set of URLs on a site that Googlebot can and wants to crawl. Google defines it as the combination of crawl capacity limit, meaning how much crawling the server can handle without slowing down, and crawl demand, meaning how much Google wants to crawl the site's URLs.

E-E-A-T (EEAT)

E-E-A-T stands for experience, expertise, authoritativeness and trustworthiness, the qualities Google's search quality raters use to judge whether a page is reliable and helpful. Google says trust is the most important of the four, and that E-E-A-T is not a specific ranking factor in itself.

Featured snippets

A featured snippet is a Google search result that reverses the usual format, showing an extract from a page first and the page's title link after it, near the top of the results. Google's systems pick the page and passage automatically when they judge the page a good answer to the query.

Google core updates

A Google core update is a significant, broad change to Google's search ranking algorithms and systems, released several times a year. Core updates don't target specific sites or pages. They change how Google assesses content overall, so some pages rise and others fall without either having broken a rule.

Google Search Console (GSC)

Google Search Console is a free Google service that shows how a website performs in Google Search and helps its owner fix problems. It reports the queries, clicks, impressions and average positions a site earns, flags crawling and indexing issues, and lets owners submit sitemaps and request indexing of new or changed pages.

hreflang

hreflang is an attribute, used with rel="alternate", that tells search engines which language and regional versions of a page exist so each searcher can be shown the right one. For example, it can point UK searchers to an en-GB page and US searchers to an en-US page with the same content.

Internal linking

Internal linking is the practice of linking from one page on a website to another page on the same site. Internal links help visitors move between related content and help search engines discover pages, understand what each one is about from its anchor text and see which pages matter most.

Keyword cannibalisation

Keyword cannibalisation happens when two or more pages on the same website target the same query and search intent, so they compete with each other in search results. Google may swap between them, or rank neither as well as a single consolidated page would, splitting links, clicks and relevance across several URLs.

Local SEO

Local SEO is the work of making a business visible in search results for people nearby, or for searches that name a place, such as 'accountant in Leeds'. It covers the business's Google Business Profile, reviews, location pages, local links and listings, and how it appears in the map results in Google Search and Maps.

Long-tail keywords

A long-tail keyword is a specific search query with low individual search volume, such as 'waterproof walking boots for wide feet' rather than 'walking boots'. Each one is searched rarely, but together they make up a large share of all searches, and they usually reveal more clearly what the searcher wants.

Meta description

A meta description is an HTML element in a page's head, written as <meta name="description" content="...">, that summarises the page for search engines. Google may show it as the snippet under a result's title link when it describes the page better than text taken from the page itself.

NavBoost

NavBoost is a Google ranking system that uses click data from past searches to adjust which results rank for a query. Pandu Nayak, a Google vice president of search, described it in the US antitrust trial against Google as one of the important signals Google has, drawing on 13 months of data.

robots.txt

robots.txt is a plain text file at the root of a website that tells crawlers which URLs they may request. It follows the Robots Exclusion Protocol, standardised as RFC 9309 in 2022. It controls crawling, not indexing: a URL blocked in robots.txt can still appear in Google if other pages link to it.

Search intent

Search intent is the goal behind a search query: what the person typing it wants to know, do or find. Matching it means giving the type of page the searcher expects, such as a guide, a product page or a local listing, rather than simply repeating the words of the query.

SERP

A SERP, short for search engine results page, is the page a search engine shows in response to a query. On Google it can mix sponsored ads, organic text results, rich results, images, videos, local listings, AI Overviews and features such as People Also Ask, and the layout changes with the query, device and country.

Technical SEO

Technical SEO is the work of making a website easy for search engines to crawl, render, index and understand, through its server set-up, code, URLs and site structure. It covers robots.txt, status codes, redirects, canonical tags, XML sitemaps, page speed, structured data and how content loads.

Title tag

A title tag is the HTML <title> element that names a page. Browsers show it in the tab, and Google uses it as the main source for the clickable headline of a search result, which Google calls the title link. Google rewrites it when it judges the title a poor description of the page.

Topical authority

Topical authority is how far search engines treat a website as an expert source on a subject, judged by how thoroughly it covers that subject and how often others cite it. Google runs a system called topic authority for news; for other sites, topical authority is an industry term rather than a named Google signal.

XML sitemap

An XML sitemap is a file that lists the URLs a site wants search engines to find, with optional details such as when each page last changed. It follows the Sitemaps protocol, which Google, Yahoo and Microsoft agreed to support jointly in 2006. It helps discovery but doesn't guarantee that pages are crawled or indexed.

Zero-click search

A zero-click search is a search that ends without the user clicking through to any website, because the answer appears on the results page or because the user stops or changes the query. Featured snippets, knowledge panels, maps, calculators and AI Overviews can all answer a query without a click.

PPC

Attribution model

An attribution model is the rule that decides how credit for a conversion is shared between the ads, clicks and channels a customer interacted with before converting. Google Ads and GA4 now use two approaches: data-driven attribution, which shares credit using machine learning, and last click, which gives all of it to the final interaction.

Broad match

Broad match is the Google Ads keyword match type that lets ads show on searches related to a keyword, including searches that do not contain its exact words. It is the default match type and reaches the widest range of searches, using signals such as the user's recent searches and the landing page content.

Click-through rate (CTR)

Click-through rate (CTR) is the percentage of people who click an ad or search result after seeing it, calculated by dividing clicks by impressions. Five clicks from 100 impressions is a 5% CTR. In Google Ads, expected CTR is one of the three components of Quality Score.

Conversion rate

Conversion rate is the percentage of ad clicks, visits or other interactions that end in a conversion, such as a sale, enquiry or sign-up. Google Ads calculates it by dividing conversions by ad interactions, so 50 conversions from 1,000 interactions is a conversion rate of 5%.

Cost per acquisition (CPA)

Cost per acquisition (CPA) is the average amount an advertiser pays in ad spend for each conversion, such as a sale, lead or sign-up. It is calculated by dividing total advertising cost by the number of conversions. Google Ads calls it cost per action and reports it as cost per conversion.

Cost per click (CPC)

Cost per click (CPC) is the amount an advertiser pays each time someone clicks an ad. In Google Ads there are three versions: max CPC is the most you are willing to pay, actual CPC is what a click is charged, and average CPC is total click cost divided by total clicks.

Cost per mille (CPM)

Cost per mille (CPM) is the price an advertiser pays for 1,000 impressions of an ad, from the Latin mille, meaning thousand. It is calculated by dividing ad cost by impressions and multiplying by 1,000, and it is the usual way to buy and compare display, video and social advertising.

Demand Gen

Demand Gen is a Google Ads campaign type that shows image and video ads across YouTube (including Shorts), Discover, Gmail, Maps and the Google Display Network to people who may be interested in a brand but are not yet searching for it. It replaced Discovery campaigns and, from 2025, Video action campaigns.

Enhanced conversions

Enhanced conversions is a Google Ads feature that improves conversion measurement by sending hashed first-party data, such as the email address or phone number a customer enters when they convert. Google matches it to signed-in Google Accounts that engaged with an ad, so it can credit conversions that cookies alone would miss.

Google Consent Mode is a way for websites and apps to pass each visitor's cookie consent choices to Google tags, so that Google Ads and Google Analytics adjust what they store and collect. Version 2, introduced in November 2023, added two signals: ad_user_data and ad_personalization.

Google Merchant Center (GMC)

Google Merchant Center is the Google platform where retailers upload and manage product data, such as titles, prices, availability and images, so their products can appear across Google. It powers free product listings on Search, the Shopping tab, Maps, YouTube and Gemini, and supplies the product data behind Shopping ads and Performance Max.

Impression share is the percentage of impressions an ad received out of the total it was estimated to be eligible for. In Google Ads, Search impression share shows how often ads appeared when they could have, and lost impression share splits the shortfall between budget and Ad Rank.

Negative keywords

Negative keywords are words or phrases an advertiser adds in Google Ads to stop ads appearing on searches that contain them. They filter out irrelevant or low-value searches, such as ones containing 'free', 'jobs' or a product the business does not sell, so budget goes on searches more likely to produce customers.

Performance Max

Performance Max is a Google Ads campaign type that runs ads across Search, YouTube, Display, Discover, Gmail and Maps from a single campaign. The advertiser supplies a conversion goal, budget, creative assets and audience signals, and Google's AI decides where, when and to whom each ad is shown.

Quality Score (QS)

Quality Score is a diagnostic rating from 1 to 10 in Google Ads that estimates the quality of a keyword's ads and landing page compared with other advertisers. It is built from three components: expected clickthrough rate, ad relevance and landing page experience, each rated above average, average or below average.

Remarketing

Remarketing is showing ads to people who have already interacted with a business, for example by visiting its website, using its app, watching its YouTube videos or giving it their email address. Google Ads now calls remarketing lists 'your data' segments, which can be targeted or excluded across Search, YouTube, Display and Gmail.

Responsive search ads (RSA)

Responsive search ads are the main text ad format in Google Ads Search campaigns. The advertiser writes up to 15 headlines and 4 descriptions, and Google combines them into ads of up to three headlines and two descriptions, choosing the combination for each search. They replaced expanded text ads in June 2022.

Return on ad spend (ROAS)

Return on ad spend (ROAS) is the revenue or conversion value earned for each pound spent on advertising, calculated by dividing conversion value by ad cost. Google Ads expresses it as a percentage, so £5 of sales from £1 of ad spend is a ROAS of 500%.

Smart Bidding

Smart Bidding is the group of Google Ads bid strategies that use Google AI to set a separate bid in each auction, aiming to maximise conversions or conversion value. The four strategies are Maximise conversions, Target CPA, Maximise conversion value and Target ROAS.

Integrated search

Incrementality testing

Incrementality testing is a controlled experiment that measures how many conversions advertising actually caused, by comparing a group exposed to the ads with a similar group that was not. The difference between the two groups is the incremental lift: the part of the results the ads can genuinely claim.

Paid and organic overlap

Paid and organic overlap is what happens when a brand's paid search ad and its organic listing appear for the same search. The key question is how many of the ad's clicks are incremental, and how many would have arrived through the organic result anyway if the ad had not run.

Search engine marketing (SEM)

Search engine marketing (SEM) is the practice of winning visibility on search engine results pages, most often through paid ads bought in an auction on platforms such as Google Ads and Microsoft Advertising. Some marketers also include SEO in the term, so agree a definition before comparing budgets or agencies.

Share of search is a brand's search volume as a percentage of the total searches for every brand in its category, usually measured with Google Trends. Les Binet presented it in 2020 as a cheap, fast metric that tracks a brand's market share and can predict where that share is heading.

Digital PR

Content syndication

Content syndication is the republishing of an article on other websites after it first appears. In digital PR it usually means a story spreading from one outlet to sister titles or partner sites. In content marketing it means licensing articles to other publishers to reach a wider audience than the original site.

Coverage tracking

Coverage tracking is the process of finding, recording and evaluating the media coverage a PR campaign earns, including the outlet, date, link status, syndicated copies and outcomes such as referral traffic. It turns a list of articles into evidence of what a campaign achieved, and it is how digital PR results are reported.

Data-led PR

Data-led PR is a digital PR approach that builds stories around original data, such as a commissioned survey, an analysis of public datasets or a brand's own anonymised figures, and offers the findings to journalists. The data gives the story news value and gives publications a reason to cite and link to the source.

Digital PR

Digital PR is the practice of earning coverage, brand mentions and links from online publications by giving journalists stories, data and expert comment they want to publish. It combines media relations with search goals, so success is measured in relevant links and visibility as well as audience reach.

Earned media

Earned media is publicity a brand gains through other people's choices rather than payment: news coverage, reviews, mentions, social shares, awards and recommendations. It is one of the four channels in the PESO model, alongside paid, shared and owned media, and carries weight because a third party, not the brand, is vouching for it.

Journalist requests

Journalist requests are call-outs from reporters, editors and podcasters looking for expert sources, data or case studies for a story. They are shared on platforms such as Qwoted, Featured, HARO and Connectively, and on social media under hashtags such as #journorequest. Answering them is a core reactive PR tactic.

Media pitch

A media pitch is a short, personalised message, usually an email, that offers a journalist a story, data, an expert or an exclusive relevant to what they cover. Unlike a press release sent to a list, a pitch is written for one reporter and explains in a few lines why their readers would care.

Newsjacking

Newsjacking is the practice of adding a brand's own angle, data or expert comment to a news story while it is still breaking, so that journalists include the brand in their coverage. The term was popularised by David Meerman Scott's 2011 book Newsjacking, and it depends on speed more than any other PR tactic.

PESO model

The PESO model is a communications framework that sorts media into four types: paid, earned, shared and owned. Gini Dietrich, founder of Spin Sucks, introduced it in 2014 to help PR and marketing teams plan advertising, media coverage, social media and their own content as one programme rather than four separate ones.

Press release

A press release is a formal written announcement that an organisation sends to journalists, and often publishes on a newswire, setting out its news with a headline, key facts, quotes and contact details. It is written for wide distribution, whereas a digital PR pitch is a short, personal note offering one journalist a story.

Reactive PR

Reactive PR is the practice of responding quickly to news, trends and journalist requests with expert comment, data or a fresh angle, rather than launching a planned campaign. It covers newsjacking, answering source requests and commenting on scheduled announcements, and it usually wins coverage within hours or days.

Unlinked brand mentions

Unlinked brand mentions are places online where a brand, product or person is named without a hyperlink to their website. They are common in news coverage. Google has said they do not pass PageRank, but they build awareness, can often be turned into links and shape what AI assistants say about a brand.

Link building

Anchor text

Anchor text is the visible, clickable text of a hyperlink. Google uses it to understand what the linked page is about and recommends anchor text that is descriptive, reasonably concise and relevant to both pages. For an image used as a link, Google reads the image's alt attribute as the anchor text.

Backlinks

Backlinks are links on one website that point to a page on another website. Search engines treat them as references between pages: Google uses links to find new pages and as a signal of relevance, and the words in a link help it understand what the linked page is about.

Broken link building (BLB)

Broken link building is a link building method that finds links on other websites pointing to pages that no longer exist, then offers the site owner a working page to link to. The publisher fixes a dead link for its readers, and the replacement page earns a link if it covers the same topic well.

Disavow file

A disavow file is a plain text list of URLs or domains uploaded to Google's disavow links tool in Search Console, asking Google to ignore those links. Google says most sites do not need one and advises using it only for spammy links that have caused, or are likely to cause, a manual action.

Domain Rating (DR)

Domain Rating (DR) is Ahrefs' score from 0 to 100 for the strength of a website's backlink profile compared with other sites in its index. Moz's Domain Authority (DA) is a similar score from 1 to 100. Both are third-party estimates built from link data, not metrics Google uses.

Guest posting

Guest posting is writing an article for another website, published under the author's name and usually including a link back to the author's own site. Google accepts guest articles written to inform the host site's readers, but treats guest posts produced mainly to build links at scale as link spam.

Link attributes

Link attributes are rel values added to a link's HTML to tell search engines what kind of link it is. Google recognises three: sponsored for paid or advertising links, ugc for user-generated content such as comments and forum posts, and nofollow when neither applies. Google treats all three as hints.

Link building

Link building is the work of getting other websites to link to your pages, through content, digital PR, outreach and partnerships that publishers choose to reference. Google uses links to discover pages and as a signal of relevance, so links from relevant, trusted sites can help pages rank and be found.

Link reclamation

Link reclamation is the process of recovering links a site has lost or never fully received. It covers redirecting links that point to deleted or moved pages, asking publishers to restore removed or mistyped links, and turning unlinked brand mentions into links, so the site keeps the value of links it already earned.

Link spam

Link spam is Google's term for creating links to or from a site primarily to manipulate search rankings. Its spam policies cover buying or selling links that pass ranking credit, excessive link exchanges, automated link creation and keyword-rich links in guest posts, and Google detects it with automated systems including SpamBrain.

Private blog network (PBN)

A private blog network (PBN) is a group of websites, often rebuilt on expired domains that still carry backlinks, run by one owner or seller mainly to link to other sites and lift their rankings. Google treats PBN links as link spam because they exist to manipulate search results, not to serve readers.

Referring domains

Referring domains are the unique websites that link to a page or site at least once. A domain that links 50 times counts as 50 backlinks but one referring domain, so the referring domain count shows how many separate sites reference a page and is a better measure of reach than total links.

Toxic backlinks

Toxic backlinks is a label SEO tools give to links they predict could harm a site's rankings, such as links from spammy, irrelevant or link-selling sites. It is not a Google term: toxicity scores come from third-party tools, and Google says its systems usually ignore spammy links without the site owner having to act.

White-label link building

White-label link building is link building carried out by a specialist provider on behalf of an agency, which sells the work to its own clients under its own brand. The client usually deals only with the agency, which remains responsible for the quality of every link and the methods used to get it.

Comparisons

AEO vs GEO

AEO and GEO overlap so heavily that many people use the terms interchangeably. Where a line is drawn, AEO is about structuring content so a system can extract a direct answer, while GEO is the wider job of getting AI systems to mention a brand, cite it and describe it accurately.

CPC vs CPM

CPC (cost per click) and CPM (cost per mille, or cost per thousand impressions) are two ways of pricing ads. With CPC you pay only when someone clicks. With CPM you pay for every 1,000 times the ad is shown, whether or not anyone clicks, so it suits awareness rather than traffic.

SEO vs GEO

SEO and GEO differ in the result each aims for. SEO earns positions in a search engine's list of links so people click through to a site. GEO earns mentions and citations inside answers written by AI systems such as ChatGPT, Gemini and Google AI Overviews, where the user may never click.

SEO vs PPC

SEO and PPC both win visibility on search results pages, but in different ways. SEO earns unpaid organic rankings, which take months to build and keep working. PPC buys ad placements through an auction, with traffic that starts as soon as ads are approved and stops when spending stops.