What is the difference between AEO and GEO?

AEO (answer engine optimization) and GEO (generative engine optimization) both describe work to improve visibility in AI answers. AEO is often used for direct-answer formats and GEO for generative engines like ChatGPT and Perplexity, but the terms overlap heavily. Google says that, for Google Search, both are still SEO.

Is AI search optimization different from SEO?

It builds on SEO rather than replacing it. Google says its AI features rely on its core ranking and quality systems, so crawl access, indexing and helpful content still come first. What changes is what you measure. You track mentions, citations and share of voice in AI answers, not only rankings and clicks.

What is the most important AI visibility metric?

There is no single best metric. Mention rate shows how often answers name you. Citation rate shows how often they link to your pages. Share of voice compares you with rivals. Many teams combine them. AnswerixAI's visibility score weights mention rate at 60%, citation rate at 25% and answer position at 15%.

Do I need an llms.txt file to appear in AI search?

Not for Google. Google says you do not need new machine-readable files, AI text files or special markup to appear in AI Overviews or AI Mode, and that Google Search ignores llms.txt. Other services may read the file. It does no harm to publish one, but it is not a proven citation lever.

What does zero-click search mean for brands?

Zero-click search means the searcher gets an answer on the results page without visiting a site. Pew Research Center found in March 2025 that Google users who saw an AI summary clicked a normal result in 8% of visits, versus 15% without one. Being named or cited inside the answer becomes more important.

AI Search Glossary: AEO, GEO and AI Terms

This AI search glossary defines the terms you need to understand answer engine optimization (AEO), generative engine optimization (GEO) and AI visibility, in plain English. Each entry gives a short definition and links to a full page in the AI visibility glossary. Terms are grouped by topic, from how engines work to how visibility is measured.

Key takeaways

AI answer engines fetch web pages, then write an answer from them, a process called grounding.
AEO and GEO are overlapping names for improving visibility in AI answers; Google calls this work SEO.
Mentions and citations are different: one names your brand, the other links to your page.
Visibility metrics compare you with rivals across a fixed set of prompts.
Crawl access and indexing still decide whether any engine can use your content.

How do AI search engines work?

AI search engines answer a question by fetching relevant pages, then writing a response grounded in those pages. Google explains this in its guide to generative AI features, which describes both retrieval-augmented generation and query fan-out.

Term	Short definition
Answer engine	An AI system that writes a direct answer instead of only listing links.
Large language model (LLM)	A model trained on large amounts of text to understand and generate language.
Retrieval-augmented generation (RAG)	A method where the model fetches documents first, then writes from them.
Grounding	Tying an AI answer to fetched sources rather than to training data alone.
Query fan-out	Running many related searches for one question to gather more sources.
Vector embeddings	Numbers that capture the meaning of text so similar ideas sit close together.
Semantic search	Search by meaning and intent rather than exact keyword match.
Hallucination	A false or unsupported statement produced by an AI model.

Google gives a clear fan-out example. For "how to fix a lawn that's full of weeds," the model might also search "best herbicides for lawns" and "remove weeds without chemicals." Each extra search is a new chance for a page to be cited. For more on RAG, see the Wikipedia article on retrieval-augmented generation.

What do AEO, GEO and AI SEO mean?

AEO, GEO and AI SEO are names for the work of improving how often AI answers mention and cite you. They overlap a great deal, and people often use them as synonyms.

Answer engine optimization (AEO) is shaping content so answer engines use it in direct answers. Wikipedia has an overview of AEO.
Generative engine optimization (GEO) is shaping content so generative engines like ChatGPT and Perplexity use it. The GEO paper by Aggarwal et al. (KDD 2024) introduced the term and found that GEO "can boost visibility by up to 40%" in generative engine responses.
AI search optimization is the broad practice of improving visibility across AI-powered search.
LLM optimization is improving how large language models understand and describe your brand.

Google's own position is that these labels describe SEO. Its guide says:

From Google Search's perspective, optimizing for generative AI search is optimizing for the search experience, and thus still SEO.

Which AI search platforms should you know?

The main AI search platforms are ChatGPT search, Perplexity, Google AI Overviews, Google AI Mode, Gemini, Microsoft Copilot and Grok. Each one finds and cites sources in its own way.

Platform	What it is
ChatGPT search	OpenAI's search feature, which finds pages with its OAI-SearchBot crawler.
Perplexity	An answer engine whose PerplexityBot crawler finds pages to link in its results.
Google AI Overviews	AI summaries shown at the top of some Google results.
Google AI Mode	Google's conversational search mode for complex questions.
Gemini	Google's AI assistant, separate from AI Overviews and AI Mode in Search.
Microsoft Copilot	Microsoft's assistant; Bing Webmaster Tools reports when it cites your pages.
Grok	The AI assistant built by xAI.

Crawler rules differ by platform. OpenAI's crawler docs say "OAI-SearchBot is used to surface websites in search results in ChatGPT's search features," while GPTBot is used for model training.

How is AI visibility measured?

AI visibility is measured by running a fixed set of prompts on each platform and recording how answers treat your brand. The core terms are below.

Term	Short definition
AI visibility	How often and how prominently a brand appears in AI answers.
AI visibility score	One number that sums up visibility across prompts and platforms.
AI mentions	Times an AI answer names your brand, product or people.
AI citations	Links in an AI answer to the pages it relied on.
AI share of voice	Your share of mentions or citations compared with rivals.
Prompt volumes	Estimates of how often people ask a given prompt.
Prompt monitoring	Tracking the same prompts and answers over time.
AI reputation	How AI answers describe and judge your brand.

A mention and a citation are not the same. An answer can name you while citing a review site, or cite your guide without naming you. Track both.

When we built AnswerixAI, our team combined these into one visibility score: 60% mention rate, 25% citation rate and 15% position in the answer, with the formula shown in the dashboard. We also label each answer that names a brand as positive, neutral or negative, with a reason.

First-party reports now exist too. Bing's AI Performance report shows citations and "grounding queries" for Microsoft Copilot. In this episode, John Mueller covers Google's Generative AI performance reporting in Search Console:

Which content and authority terms matter?

Content and authority terms describe what makes a page worth citing and a brand worth naming. These are the ones that come up most.

Term	Short definition
E-E-A-T	Experience, expertise, authoritativeness and trustworthiness, Google's quality framework.
Brand authority	The trust a brand has across AI systems, search engines and the web.
Knowledge graph	A structured map of entities and how they relate.
Entity recognition	How AI systems spot and classify people, companies and products.
Structured data	Machine-readable labels that describe what a page contains.
Schema markup	Structured data written with the schema.org vocabulary.
Topic clusters	Groups of linked pages that cover one subject in depth.
Content freshness	How current and accurate the facts on a page are.

Google's helpful content guidance says of E-E-A-T: "Of these aspects, trust is most important." For how Google's own entity database works, see the Wikipedia article on the Knowledge Graph. To put these terms to work, read our guide on brand authority in AI search.

Which technical terms affect AI access?

Technical terms describe whether engines can reach, read and store your pages. If these fail, no content work will help.

AI crawlers are bots that fetch web pages for AI models and answer engines, such as OAI-SearchBot and PerplexityBot.
Indexability is whether a page can be crawled and stored in a search index. Google says a page must be "indexed and eligible to be shown in Google Search with a snippet" to appear as a link in AI Overviews or AI Mode, per its AI features docs.
llms.txt is a proposed file that lists a site's key pages for language models. Google says Google Search ignores it.
Zero-click search is when a searcher gets the answer without visiting a site.

Zero-click behaviour is measurable. A Pew Research Center study of 68,879 Google searches by 900 U.S. adults in March 2025 found that about one in five searches produced an AI summary. Users who saw one clicked a normal result in 8% of visits, versus 15% without one.

Which AI search terms are most often confused?

Several pairs of AI search terms sound alike but mean different things. Mixing them up leads to wrong fixes, such as blocking the wrong crawler.

Pair	The difference
Mention vs citation	A mention names your brand in the text. A citation links to your page as a source.
GPTBot vs OAI-SearchBot	OpenAI uses GPTBot for model training and OAI-SearchBot for ChatGPT search results.
AI Overviews vs AI Mode	AI Overviews add a summary to normal results. AI Mode is a separate conversational search mode.
AEO vs GEO	Both mean improving visibility in AI answers; the names come from different groups.
Domain authority vs brand authority	Domain authority is a third-party link score. Brand authority is how far engines trust and name you.
llms.txt vs robots.txt	robots.txt controls crawler access. llms.txt is an optional list of key pages.

The crawler pair matters most in practice. Blocking GPTBot does not remove you from ChatGPT search. OpenAI says sites opted out of OAI-SearchBot "will not be shown in ChatGPT search answers, though can still appear as navigational links." OpenAI says robots.txt changes take "~24 hours" to reach its systems.

Which AI visibility tool terms should you know?

Tool terms describe the software used to track and act on AI visibility. They map to features you will see in most platforms.

Citation monitoring tracks which sources AI answers cite for your prompts. In AnswerixAI, Citations Monitoring splits them into your site, competitors and third parties.
AI traffic analytics measures visits that arrive from AI assistants such as ChatGPT, Perplexity, Gemini and Copilot.
MCP server exposes tools and data to AI agents through the Model Context Protocol, so a client like Claude Code can query your data.
Site audit scores a page against a set of signals. AnswerixAI's Site Audit scores a public URL from 0 to 100 on 47 AEO and GEO signals.

Where can you learn more?

Browse the full AI visibility glossary for every term, grouped by category. For practical next steps, start with how to get more AI citations and then plan your pages with our guide to an AI content strategy that gets cited.

AI Search Glossary: AEO, GEO and AI Visibility Terms