The help sections are organized like a book into chapters. This should not surprise you, since the same source is used both for the printed manual and the online help. Just as you can flip through the pages of a book there are special commands to browse through the help sections.
?
?<
The two help commands ?< and ? correspond to the flipping of pages.
?< takes you to the section preceding the current section and displays
it, and ? takes you to the section following the current section.
?<<
?
?<< is like ?<, only more so. It takes you back to the first
section of the current chapter, which gives an overview of the sections
described in this chapter. If you are already in this section ?<<
takes you to the first section of the previous chapter. ? takes you
to the first section of the next chapter.
?-
?+
GAP remembers the sections that you have read. ?- takes you to the
one that you have read before the current one, and displays it again.
Further ?- takes you further back in this history. ?+ reverses this
process, i.e., it takes you back to the section that you have read
after the current one. It is important to note, that ?- and ?+ do
not alter the history like the other help commands.
GAP 3.4.4