Texinfo is the official documentation format of the GNU project. It was invented
by Richard Stallman and Bob Chassell many years ago, loosely based on Brian
Reid's Scribe and other formatting languages of the time. It is used by many
non-GNU projects as well.

Texinfo uses a single source file to produce output in a number of formats, both
online and printed (dvi, html, info, pdf, xml, etc.). This means that instead of
writing different documents for online information and another for a printed
manual, you need write only one document. And when the work is revised, you need
revise only that one document. The Texinfo system is well-integrated with GNU
Emacs.

WWW: https://www.gnu.org/software/texinfo/
