What is the difference between SEO, AEO and GEO?

SEO, AEO, and GEO are best viewed as complementary parts of the same search strategy.
SEO (Search Engine Optimization) focuses on helping webpages become discoverable, understandable, and competitive in traditional search results. This includes technical SEO, content quality, internal linking, metadata, site architecture, authority signals, and local optimization.
AEO (Answer Engine Optimization) focuses on making information easy for search engines and answer systems to extract and present as a direct answer. Clear headings, concise definitions, FAQs, structured data, entity relationships, and well-organized content all help.
GEO (Generative Engine Optimization) focuses on helping brands and content become understandable and useful to AI-powered search and generative systems. That means publishing authoritative information, clearly establishing entities and expertise, using supporting evidence, maintaining consistent brand information, and creating content that can be confidently referenced when an AI system constructs an answer.
For an agency, I would not build three completely separate strategies. Start with a technically strong SEO foundation, structure the content so important questions can be answered clearly, and then strengthen the entities, expertise, citations, schema, and supporting information that make the content useful to both traditional search engines and generative systems.
A practical way to verify the strategy is to monitor traditional rankings and Search Console performance while also testing whether the brand and its content appear accurately in AI-generated answers, AI Overviews, and answer-engine responses.