They are indeed described in the manual, here. Descriptions of this sort of thing should be relatively easily findable on pages that cover their area – if you didn’t know what this was called, you could for instance look at the overview of Write mode for a pointer.
They allow you to access either panels or popovers from the toolbox. Some notations have both a panel and popover equivalent, others have only one or the other. This panel/popover switch makes it possible always to access popovers directly from the UI, in addition to the key commands.
Tooltips are unavailable in the Notations toolbox at the moment for technical reasons.