C-h p (or M-x finder-by-keyword) gives you a finder-mode buffer with lisp libraries shown under keyword categories, so you can look at say all the “games” related things. Read more in finder-by-keyword.
Selecting a library shows its commentary with FinderCommentary (which can be used directly too, and on anything in your LoadPath).
The libraries listed come from finder-inf.el. Normally it’s only things supplied with Emacs, not ‘site-lisp’ or personal extras. Advanced users can try finder-compile-keywords to make a new finder-inf.el with everything in your LoadPath.
See Also:
finder.el: multiple commentary buffers, font-locking, syntax tablefinder-inf.el updated on Debian