Documentation about macros and packages

Command: TeX-documentation-texdoc

(C-c ?) Get documentation about the packages installed on your system, using texdoc to find the manuals. The function will prompt for the name of packages. If point is on a word, this will be suggested as default.

If the command is called with a prefix argument, you will be shown a list of manuals of the given package among to choose.

The command can be invoked by the key binding mentioned above as well as the ‘Find Documentation...’ entry in the mode menu.

Note that this command assumes TeX Live, not MiKTeX; according to ‘Texdoc’ site,

A command named texdoc is also available in MiKTeX, but it is merely a shortcut for an independent program, mthelp.

Thus it isn’t sure whether this command works for MiKTeX or not.