A mind map shows the shape of a note: the main ideas, what hangs off them, and how deep each branch goes. Mind maps are part of the Pro and Lifetime plans.
Creating one
Open the note. On desktop, type / and choose Mind Map. On mobile, open the apps group on the toolbar and choose Mind Map. Generating builds the map from the note content, and the map stays attached to the note.
Exploring it
Pan around, zoom, and expand or collapse branches node by node, or all at once with the expand all and collapse all controls. The map remembers which branches you collapsed.
Mind map or graph view
They answer different questions. A mind map is the close up, the structure inside one note. Graph view is the wide shot, how notes across the whole library link to each other. Studying a topic, you want the mind map; checking coverage of a course, you want the graph.
What makes a good map
The map mirrors the note structure, so headings and short paragraphs produce clean branches. A note that is one long paragraph gives the map very little to work with.