Texinfo is a documentation system that uses a single source file to
produce both on-line information and printed output.  This means that
instead of writing two different documents, one for the on-line help
or other on-line information and the other for a typeset manual or
other printed work, you need write only one document.  When the work
is revised, you need revise only one document.  You can read the
on-line information, known as an "Info file", with an Info
documentation-reading program.  By convention, Texinfo source file
names end with a `.texi' or `.texinfo' extension.  Texinfo is
described in the Texinfo Manual.
You can write and format Texinfo files into Info files within GNU
Emacs, and read them using the Emacs Info reader.  If you do not have
Emacs, you can format Texinfo files into Info files using `makeinfo'
and read them using `info'.  Use TeX, which is not included in this
package, to typeset Texinfo files for printing.