GEO glossary: 30 terms for the AI-search era
The short answer
This glossary defines the core terms of the AI-search era in plain language — Generative Engine Optimization (GEO), Answer Engine Optimization (AEO), retrieval-augmented generation (RAG), AI Overviews, llms.txt, AI share of voice, and the rest. Use it as a quick reference when planning or measuring your AI-search visibility.
Key takeaways
- GEO is the practice of earning citations inside AI-generated answers.
- RAG is the retrieval step that lets engines ground answers in your content.
- Citation and AI share of voice replace clicks and rankings as core GEO metrics.
- Most terms describe parts of one system: retrieve, synthesize, cite, measure.
On this page · 4 sections
Core concepts
Start with the terms that frame the whole field.
- Generative Engine Optimization (GEO): structuring content so AI answer engines cite your brand as a source.
- Answer Engine Optimization (AEO): structuring a passage to be extracted as the direct answer, on snippets, voice, or AI surfaces.
- Answer engine: any system that returns a synthesized answer instead of a list of links (ChatGPT Search, Perplexity, AI Overviews).
- Generative engine: an AI system that composes a new answer from retrieved sources rather than quoting one.
- Citation: a named, linked source the engine attributes part of its answer to — the GEO win condition.
How engines find and use content
These terms describe the retrieval and grounding machinery behind an AI answer.
- Retrieval-augmented generation (RAG): retrieving relevant content at query time and grounding the generated answer in it.
- Retrieval: the step where an engine searches an index and pulls candidate passages relevant to the query.
- Chunk: a passage-sized piece of your content that gets indexed and retrieved independently.
- Embedding: a numeric vector representing a chunk's meaning, used to match it to a query.
- Grounding: anchoring a generated answer to retrieved evidence to keep it accurate and citable.
- Hallucination: a confident but unsupported or false statement a model produces without grounding.
- Parametric knowledge: what a model learned during training, frozen at its cutoff date.
Surfaces and crawlers
Where AI answers appear, and the bots that fetch the content behind them.
- AI Overview: Google's AI-generated summary at the top of results, synthesized from its index and linked to sources.
- Featured snippet: a single source quoted verbatim at the top of results.
- Zero-click search: a search satisfied on the results surface, with no click to a site.
- llms.txt: a proposed plain-text file that points AI crawlers to your most important, answer-ready pages.
- robots.txt: the file that allows or blocks crawlers — including AI bots — from fetching your pages.
- GPTBot / OAI-SearchBot: OpenAI's crawlers; allow them to be eligible for ChatGPT Search citations.
- PerplexityBot: Perplexity's crawler; allow it to be eligible for Perplexity citations.
- Structured data (JSON-LD): machine-readable markup stating a page's entities and facts so engines parse it cleanly.
Strategy and measurement
The terms you'll use to plan content and prove impact.
- AI share of voice: how often you're cited versus competitors for your target questions.
- Answer-first content: writing that states the direct answer near the top, before context.
- Entity SEO: making your brand a clear, consistent entity engines can recognize and disambiguate.
- Topical authority: depth and breadth across a subject that signals you're a trusted source on it.
- E-E-A-T: experience, expertise, authoritativeness, and trustworthiness — quality signals engines lean on.
- Brand Memory: a consistent source of truth about your business that grounds accurate AI descriptions of it.
- Share of model: a brand's presence across AI answers for a category, the AI-era analog of share of search.
Frequently asked questions
What's the difference between GEO and AEO in one line?
AEO makes a passage extractable as the answer; GEO is the broader practice of earning citations across AI engines, which includes AEO plus authority and machine-readability.
Is llms.txt an official standard?
It's a community proposal, not a universally adopted standard. It's low-cost to add and can help AI crawlers find your best pages, but on its own it doesn't guarantee citations.
Which term should I track as my main GEO metric?
AI share of voice — how often you're cited versus competitors for your target questions — is the closest single measure of GEO success, complemented by AI-referral traffic and leads.
Keep reading
GEO fundamentals
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Does GEO work for small businesses?
Does GEO work for small businesses? Yes - and often better than for big brands, because AI answers reward specific, niche expertise over sheer size and budget.
How long does GEO take to show results?
How long does GEO take to work? Expect early citation signals in weeks and meaningful momentum over 2-4 months - faster than classic SEO, but not instant.
Is GEO worth it? An honest assessment
Is GEO worth it? An honest take: for most businesses whose buyers use AI search, yes - but the return depends on your audience, niche, and willingness to do it well.
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