It's described in the remainder of the point - they use an LLM to generate additional search queries, either rephrasings of the user's query or bringing additional context from the chat history.
One of the key features in Claude Code is "Agentic Search" aka using (rip)grep/ls to search a codebase without any of the overhead of RAG.
Sounds like even RAG approaches use a similar approach (Query Generation).
Or am I completely misunderstanding how Claude Code works?