It used to be documented more clearly. Now we have this:
On the left side of the above page, you can do a lot of scrolling to find the page entry and you may note that there are other interesting things about text, as well scattered as is possible to scatter them, with no overall quick-reference that links to them. In the 'old' days they had a book of contiguous pages, so if you wanted to know about notes you needed only to find one of the pages and the others were nearby, available to read as fast as you could.