AI architecture
Retrieval Augmented Generation (RAG)
Also: RAG, retrieval augmented generation
RAG separates live retrieval from what a model learned in training. Training data changes only when a new model ships. Retrieval can pick up a page soon after it is crawled.
Each AI app retrieves from different places. ChatGPT search uses OpenAI's own crawling (OAI-SearchBot) together with outside search providers. Gemini and Google AI Mode draw on Google's index. Perplexity runs its own crawler. The sources each app cites for the same question often differ, which is why results must be measured per app.