Texinfo is the official documentation format of the GNU project. It uses a single source file to produce output in a number of formats, both online and printed (dvi, info, html, 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. Some features need texlive (unnecessary if only the info command is used).

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