what it is
You load sources into a notebook (PDFs, docs, web pages, YouTube videos) and it answers questions from those sources with citations. It can also turn a notebook into an audio overview. Google now serves it at notebook.google under the name Gemini Notebook.
how I use it
I use it for source-grounded research and drive it from the terminal with the nlm CLI, so Claude Code can build and query notebooks. The full loop is in NotebookLM + Claude Code + Obsidian Loop.