GNU Emacs Lisp Reference Manual
GNU Emacs Lisp has convenient on-line help facilities, most of which
derive their information from the documentation strings associated with
functions and variables. This chapter describes how to write good
documentation strings for your Lisp programs, as well as how to write
programs to access documentation.
Note that the documentation strings for Emacs are not the same thing
as the Emacs manual. Manuals have their own source files, written in
the Texinfo language; documentation strings are specified in the
definitions of the functions and variables they apply to. A collection
of documentation strings is not sufficient as a manual because a good
manual is not organized in that fashion; it is organized in terms of
topics of discussion.