finder-commentary is a function that displays the commentary section of an Emacs library. Simply type
‘M-x finder-commentary RET’ and it prompts you for the library name. The name of the library can be both
‘name’ and `name.el’. This prompt uses completing-read, which means that you can press TAB to try for completions.
‘q’ to exit finder-commentary, and
‘d’ to see a list of available topics (in FinderMode).
finder-commentary can be very useful, as you don’t need to locate the library to see its documentation, it only needs to be in your load-path (see LoadPath).
Some library authors are very good at writing helpful Commentary sections, while a few others don’t include them at all. Some include a URL, a changelog, TODO, names of author(s), etc.
The commentary section is placed at the beginning of the library, usually right after any license, and looks something like this:
;;; Commentary: ;; ;; This module provides an Emacs interface to <something>.