Glossary · GEO and AI visibility

The GEO and AI visibility glossary: 18 terms, defined simply

From citation to share of voice, from grounding to llms.txt: the vocabulary you need to understand and improve how AI assistants such as ChatGPT, Gemini, Claude, Perplexity and Grok talk about your brand. Written for marketers, SEO leads and founders — each definition is a few plain sentences, with a link to go deeper when we cover the term in depth. Last updated: June 12, 2026.

Part 1 · The discipline

The discipline and its engines

GEO (Generative Engine Optimization)

Generative Engine Optimization is the practice of making a brand visible and well described in the answers written by AI assistants such as ChatGPT, Gemini, Claude, Perplexity and Grok. Where SEO targets a position in a list of links, GEO targets the content of a single generated answer: being cited, recommended and named early. It combines content structure, third-party authority and continuous measurement.

Go deeper: the complete GEO guide →

AEO (Answer Engine Optimization)

Answer Engine Optimization is a near-synonym of GEO: optimizing content so that answer engines select it and cite it. The term appeared earlier, around featured snippets and voice assistants, before generated answers became the norm. In practice, AEO and GEO now describe the same discipline, and the two acronyms are used interchangeably.

Answer engine

A system that replies to a question with a single written answer instead of a list of links to explore. ChatGPT, Gemini, Claude, Perplexity and Grok all behave as answer engines: the user reads a synthesis and rarely clicks through to the sources. For a brand the consequence is binary — absent from the answer, you are invisible, whatever your traditional rankings.

AI visibility

How present a brand is in AI assistant answers across the questions that matter for its business: whether it is cited at all, how often, at what position and against which competitors. Unlike a Google ranking, AI visibility cannot be read off a results page; it has to be measured by asking the engines real customer questions and analyzing the generated answers.

See how AI visibility is measured →

Part 2 · Metrics

The signals and metrics of AI visibility

Citation

A citation is when an AI assistant names your brand or your site in its answer, as an option or as a source. It is the base unit of AI visibility: counted across many questions, several engines and repeated runs, citations become a citation rate — how often you appear when your market is discussed. On source-backed engines such as Perplexity, a citation often comes with a link to the page the answer relied on.

How we count citations →

Mention

The weakest visibility signal: your brand appears somewhere in the text of the answer, sometimes in passing or in a list among others. A mention proves the model knows you exist, but says nothing about how favorably or how prominently you are presented. Tracking separates mere mentions from actual recommendations.

Recommendation

The strongest visibility signal: the assistant explicitly advises the user to choose or try your brand for their need. Recommendations weigh directly on buying decisions, because the user asked for a shortlist and your name is in it. Moving a brand from occasional mention to consistent recommendation is the practical goal of GEO work.

AI share of voice

Your brand's relative weight in AI answers compared with the competitors cited on the same panel of questions, consolidated across engines and runs. A brand cited often and early weighs more than one mentioned rarely and last. It is a relative metric, specific to the panel tested: useful to track progress against competitors, not a universal ranking of the web.

Go deeper: our AI share of voice guide →

Average position (in AI answers)

Where your brand appears inside the generated answer, averaged across questions and runs: named first, somewhere in the middle, or as a trailing mention. Position matters because users read a single answer from the top — the first option named captures most of the attention. It is the AI-answer equivalent of a ranking position in classic SEO.

How position is measured →

Prompt tracking (trigger prompts)

Monitoring a fixed panel of real customer questions — prompts — over time, to see which ones make the assistants cite your brand and which cite competitors instead. The questions that surface your brand are called trigger prompts; those that ignore you show where to act. Keeping the panel stable is what makes measurements comparable from one period to the next.

Everything you can track →

Part 3 · Under the hood

How AI engines build their answers

Grounding

The mechanism by which an AI engine bases its answer on documents retrieved at question time — typically live web results — instead of relying only on its training data. Gemini, for example, can ground its answers with Google Search results. Grounding matters for GEO because grounded answers can cite fresh pages: content you publish today can influence answers without waiting for a model retrain.

RAG (Retrieval-Augmented Generation)

Retrieval-Augmented Generation is a two-step architecture: the system first retrieves relevant documents, then has the language model write its answer from them. Most answer engines that cite their sources, such as Perplexity, follow this pattern. RAG is why GEO advice insists on self-contained, extractable passages: retrieval selects fragments of pages, not whole sites, so each section must stand on its own.

Hallucination

When a language model states something false with full confidence — an invented fact, a wrong figure, a feature your product never had. Hallucinations happen because models generate plausible text rather than verified truth. For a brand, the risk is being described inaccurately in answers prospects trust; monitoring what assistants actually say about you is the first line of defense.

Knowledge cutoff

The date where a model's training data stops: without web access, the assistant knows nothing more recent. This is why a recently launched brand can be invisible to a model answering from memory, while engines that search the live web can pick it up within days. GEO therefore works on two fronts — the footprint models memorize at training time, and the pages retrieval can find right now.

AI Overviews

Google's AI-generated summaries shown above the classic results for some searches, with links to supporting sources. They belong to the same shift from lists of links to generated answers that GEO addresses. Note that GEO console does not query AI Overviews: our measurements cover ChatGPT, Gemini, Claude, Perplexity and Grok.

Part 4 · Groundwork

Preparing your site for AI engines

llms.txt

A proposed standard: a Markdown file served at the root of your site (/llms.txt) that gives language models a concise, curated map of your most important content. It plays for AI assistants a role comparable to robots.txt and sitemap.xml for crawlers. Engine adoption is still uneven, but the file is cheap to add and makes your site easier to read for the systems that quote it.

Go deeper: our llms.txt guide →

AI crawler (GPTBot, ClaudeBot, PerplexityBot)

A bot an AI company uses to read web content, either to train its models or to fetch pages live while composing an answer. The best known are GPTBot (OpenAI), ClaudeBot (Anthropic) and PerplexityBot (Perplexity). Blocking them in robots.txt keeps your content out of the engines — and out of the answers; letting them in is usually the first technical step of GEO.

Check that AI crawlers can read your site →

Answer-first content

A writing structure where the complete, direct answer to the reader's question comes first — typically in the opening paragraph — with context and details after. Answer engines favor passages they can quote as they stand, so answer-first pages are easier to extract and cite. It is the editorial backbone of most GEO recommendations, including the page you are reading.

Go deeper: how to get cited by the engines →

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