Glossary
AI Search Glossary
Plain definitions for the 25 terms that come up when B2B teams start working on AI search. Each entry gives the definition first, then what it means in practice, why it matters to a buyer, and how to act on it. Sources are linked where a claim is not ours.
AI Crawler
An AI crawler is a bot operated by an AI provider that fetches web pages either to train models or to answer live user queries. Each is identified by a user agent and can be allowed or blocked in robots.txt; OpenAI, for example, documents separate agents for training and for user-triggered browsing.
AI Search Visibility
AI search visibility is how often, and how favourably, AI engines mention, cite and recommend a brand across a defined set of buyer prompts. It is measured against a fixed prompt list run repeatedly across engines, so movement over time reflects your position rather than a change in the questions asked.
AI Share of Voice
AI share of voice is your brand's proportion of all brand mentions returned across a fixed prompt set. If ten prompts return sixty brand mentions and twelve of them are yours, your share of voice is twenty per cent. It is a relative measure, so it moves when competitors move too.
Answer Engine Optimization (AEO)
Answer engine optimization is the practice of structuring content so an answer engine can extract a single direct response and attribute it to your brand. It targets surfaces that resolve a question in place — AI Overviews, featured snippets, People Also Ask and assistant replies — rather than a ranked list of links.
Brand Mention
A brand mention is any appearance of your name in an AI answer, linked or unlinked. It is the weakest of the three visibility outcomes: it confirms the engine associates you with the topic, but it says nothing about whether the engine trusts your content or would suggest you to a buyer.
Chunking
Chunking is splitting a document into smaller passages so a retrieval system can fetch and quote the part that answers a question rather than the whole page. Engines retrieve chunks, not sites, which means the unit that competes for a citation is a section of your page.
Citation (AI Search)
A citation in AI search is the attributed link an engine attaches to a claim inside its answer, crediting the source the statement came from. Citation is stronger than a passing mention because it is verifiable and clickable, and weaker than a recommendation because it credits a fact rather than endorsing you.
E-E-A-T
E-E-A-T stands for experience, expertise, authoritativeness and trust. Google describes it in its search quality rater guidelines as a way of assessing content quality, with trust the most important element. It is not a direct ranking score, but it names the signals that credible content tends to carry.
Embedding
An embedding is a numeric vector that represents the meaning of a piece of text, so systems can compare passages by similarity rather than exact keyword match. Retrieval layers in AI search embed both the question and candidate content, then select passages whose vectors sit closest to the query.
Entity
An entity is a distinct thing that search and AI systems recognise and store attributes about: a company, product, person, place or concept. Engines answer brand questions from entity understanding, so if your attributes are inconsistent across the web the engine's picture of you is inconsistent too.
Featured Snippet
A featured snippet is the block at the top of Google's results that quotes an extract from a page in order to answer the query directly, with a link to the source. Google says these are selected programmatically from pages that appear in the results, not submitted by site owners.
Generative Engine Optimization (GEO)
Generative engine optimization is the practice of shaping content, sources and entity data so generative AI engines retrieve it, quote it and attribute it when answering a user. The term was introduced in a 2024 research paper that tested which content changes raise a source's visibility inside generated answers.
Google AI Overviews
AI Overviews are Google's AI-generated summaries that appear above the traditional results for some queries, with links to the pages the summary drew on. Google describes them as using a customised version of Gemini to surface information alongside the links it cites.
Grounding
Grounding is tying a model's output to verifiable external sources so each claim in the answer can be attributed and checked. A grounded answer names where its statements came from; an ungrounded one is produced from the model's own parameters and cannot be traced back to any document.
Hallucination
A hallucination is a confident but false statement produced by a language model. For brands this shows up as invented pricing, discontinued products, wrong leadership names or misattributed positioning — errors that read as authoritative and are repeated to buyers who have no way to check them.
Knowledge Graph
A knowledge graph is a structured network of entities and the relationships between them — company to founder, product to category, brand to competitor. Search systems use graphs to answer questions about things rather than text strings, and AI answers inherit those relationships when describing a brand.
Large Language Model (LLM)
A large language model is a neural network trained on very large text corpora to predict language, and it is what produces the prose in ChatGPT, Gemini, Perplexity and Copilot. Left alone it answers from training data; connected to search or a document store it answers from retrieved sources instead.
LLM SEO
LLM SEO is the practice of making a brand retrievable, quotable and recommendable inside large language model answers. LLM SEO, LLMO and generative engine optimization are different names for the same work; the vocabulary varies by vendor, the underlying activity — content, entity and citation engineering — does not.
llms.txt
llms.txt is a community proposal for a markdown file at a site's root that offers language models a curated, readable summary of the site's most important content. It is a proposal published at llmstxt.org, not a standard adopted by search or AI providers, and support should not be assumed.
Prompt Set
A prompt set is the fixed, documented list of buyer questions run repeatedly across AI engines to measure visibility. Because AI answers vary between runs, the prompt list must stay constant for results to be comparable: change the questions and you have started a new baseline rather than continued the old one.
Recommendation (AI Search)
A recommendation is when an AI engine actively names your brand as an option a buyer should consider, rather than merely quoting you as a source. Mention, citation and recommendation form a ladder: mention is presence, citation is evidence, recommendation is endorsement, and only the last one shapes a shortlist.
Retrieval-Augmented Generation (RAG)
Retrieval-augmented generation is an architecture that fetches relevant documents at query time and passes them to a language model, which then answers from that material. It was introduced in a 2020 research paper and is the mechanism behind AI answers that carry live citations to specific web pages.
Structured Data (Schema Markup)
Structured data is standardised machine-readable markup — usually schema.org vocabulary in JSON-LD — that tells machines what a page's visible content means. Google's documentation is explicit that structured data must describe content that is actually visible to users on the page.
Vector Search
Vector search retrieves content by comparing embeddings, matching passages on meaning rather than exact wording. It lets an engine surface a relevant passage even when the buyer's phrasing shares no keywords with the page, which is why AI answers often quote content that never targeted the query as written.
Zero-Click Search
A zero-click search is a query resolved on the results page or inside an AI answer, so the user never visits a website. The information still comes from published sources, which means the commercial question shifts from how much traffic a page earns to how often it is the source being read.
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