How are the Craft docs created?
There is a Documentation structured section with three entry types.


Heading Only
Page
Link


The Getting Started, Core Concepts, etc. headers are the Heading Only entry type. The only field is has is a title.

The majority of the docs are using the Page entry type.

The Link entry type is used for the entries like Full Templating Reference and Plugin Development that open into a new window, and those are their own separate structured sections.