In this channel's material, source guide names the auto-generated summary that NotebookLM produces for each document you load into a notebook. When you open a source, the tool has already written a guide to it, so you get a fast orientation of what the document contains before reading it end to end [^01a0f15b-0d23-7d8c-85d9-5c11230b9d2a@884]. The demos treat the source guide as a per-source orientation layer that sits alongside the other auto-generated artifacts — inline citations, the checkbox source selection, and the notebook-wide Notebook Guide with its FAQs, study guides, and timelines [^01a0f15b-0d23-7d8c-85d9-5c11230b9d2a@1863]. Worth noting the caveat stated plainly in the source: a source guide is very useful for a single-topic document, but far less useful for a grab-bag source such as a notebook holding hundreds of loosely related quotes [^01a0f15b-0d23-7d8c-85d9-5c11230b9d2a@884]. In practice it serves the same orient first, then dive in habit modeled in the live NASA-transcripts session: skim the guide, then move on to querying, pinning notes, and hunting for connections.