RAG is why fresh, well-structured web content can influence an AI answer even when the model was trained long ago. Instead of relying only on what it memorized, the engine searches a live index, pulls the most relevant passages, and writes its answer from them, often citing the sources.
For GEO, RAG is the opportunity. If your content is retrievable (indexed, clearly written, structured) and authoritative, it can become one of the passages the model grounds its answer in. Perplexity and Google AI Overviews lean heavily on retrieval, which is why content quality and structure move the needle there quickly.