Using Texinfo, you can create a printed document with the normal features of a book, including chapters, sections, cross references, and indices. From the same Texinfo source file, you can create a menu-driven, online Info file with nodes, menus, cross references, and indices. You can also create from that same source file an HTML output file suitable for use with a web browser, or an XML file. The GNU Emacs Manual is a good example of a Texinfo file, as is this manual.
To make a printed document, you process a Texinfo source file with the TeX typesetting program (but the Texinfo language is very different from and much stricter than TeX's usual languages, plain TeX and LaTeX). This creates a DVI file that you can typeset and print as a book or report (see Hardcopy).
To output an Info file, process your Texinfo source with the
makeinfo utility. You can install the result in your Info tree
(see Installing an Info File).
To output an HTML file, run makeinfo --html on your Texinfo
source. You can (for example) install the result on a web site.
To output an XML file, run makeinfo --xml on your Texinfo source.
To output DocBook (a particular form of XML), run makeinfo
--docbook. If you want to convert from Docbook to Texinfo,
please see http://docbook2X.sourceforge.net/.
TeX works with virtually all printers; Info works with virtually all computer terminals; the HTML output works with virtually all web browsers. Thus Texinfo can be used by almost any computer user.
A Texinfo source file is a plain ASCII file containing text
interspersed with @-commands (words preceded by an @)
that tell the typesetting and formatting programs what to do. You may
edit a Texinfo file with any text editor; but it is especially
convenient to use GNU Emacs since that editor has a special mode,
called Texinfo mode, that provides various Texinfo-related features.
(See Texinfo Mode.)
Before writing a Texinfo source file, you should learn about nodes, menus, cross references, and the rest, for example by reading this manual.
You can use Texinfo to create both online help and printed manuals; moreover, Texinfo is freely redistributable. For these reasons, Texinfo is the official documentation format of the GNU project. More information is available at the GNU documentation web page.