You’re thinking of retrieval augmented generation (RAG) with a vector database. Its something that’s being actively developed. I haven’t had time to dig much into it, especially currently. But the terms themselves should give you a starting point.

Edit: a quick google gives what could be a promising starting point https://huggingface.co/learn/cookbook/rag_llamaindex_librarian

Not only that but between the various web tracking technologies that advertisers use and people’s reuse of credentials for convenience you now have an easier way to associate a real identity with a specific person as they browse the internet. A boon to advertisers and other interested parties alike.