SEO, GEO, AEO, AIO, REG and RAG

The terms describe different parts of search, answers, identity and retrieval. They overlap, but they are not interchangeable.

Quick comparison

Term	Full name	What it focuses on	Who usually applies it
SEO	Search Engine Optimization	Crawling, indexing, relevance and search visibility	Site owners, publishers, marketers and developers
GEO	Generative Engine Optimization	Usefulness and visibility in generated answers	Publishers, marketers and organizations
AEO	Answer Engine Optimization	Clear responses to direct questions	Publishers, marketers, support teams and educators
AIO	AI Optimization or AI Overviews	Depends on context; the acronym has more than one meaning	Marketers, publishers and product teams
REG	Recognition and Retrieval Engine Guidance	Correct entity recognition and accurate information retrieval	Businesses, publishers and data stewards
RAG	Retrieval-Augmented Generation	AI systems retrieving outside information before generating an answer	AI engineers and product teams

SEO: the foundation

Search Engine Optimization helps search engines discover and understand pages and helps people find useful content through search results.

SEO includes technical crawl access, indexing, page structure, content, internal links, local information and reputation. Google states that the same SEO fundamentals remain relevant to its generative search features.

GEO: generated-answer visibility

Generative Engine Optimization focuses on whether content or an entity can be understood and used when an AI-assisted search system creates a generated response.

GEO can include direct definitions, original evidence, reliable sourcing, authorship, clear entity information and content that addresses the full question.

AEO: direct answers

Answer Engine Optimization presents accurate information in a form that directly satisfies a specific question.

AEO is not simply adding an FAQ. It means answering the actual customer question immediately, then explaining the details, conditions and exceptions needed to use the answer correctly.

AIO: define the acronym

AIO can mean AI Optimization or AI Overviews. The writer should state which meaning is intended.

AI Optimization can be a broad umbrella for work intended to improve visibility or performance around AI systems. AI Overviews is the name of Google’s generated summary feature in Search.

REG: recognition and retrieval

Recognition Engine Guidance and Retrieval Engine Guidance is Dean Jessop’s framework for helping systems identify the correct business or entity and retrieve accurate, relevant information about it.

REG was developed through IRefer Club. It is an original framework—not an official Google, OpenAI or schema.org standard.

See how IRefer applies modern visibility principles →

RAG: a technical AI architecture

Retrieval-Augmented Generation is a technical approach in which an AI application retrieves external information and provides it to a language model while the model generates a response.

RAG is implemented by developers inside an AI product. A business owner cannot install RAG into Google or ChatGPT, but the owner can publish information that a retrieval system may later find.

Read the complete terminology guide

This page provides the book-level overview. AI Search Explained contains dedicated pages, a full comparison and practical examples.

Open AI Search Explained

Sources and further reading

Google SEO Starter Guide — Official guidance on SEO fundamentals.
Google’s guide to generative AI features in Search — Official guidance on SEO and AI Overviews/AI Mode.
GEO research paper — The research paper that formalized Generative Engine Optimization.
RAG research paper — The research paper that introduced Retrieval-Augmented Generation.