You can read the documentation for GNU software either with printed manuals or, using an ordinary ASCII terminal, as online info files. You can browse through the online documentation with GNU Emacs or with the program info, a smaller program intended just for the purpose of viewing info files. This documentation describes version 2.14 of info.
To learn how to view and read documentation with info, see Command Line Options, Moving the Cursor, Moving Text Within a Window, and Selecting a New Node.
To learn how to use info, see Searching an Info File, Selecting Cross References, Parts of an Xref, Selecting Xrefs, Manipulating Multiple Windows, The Mode Line, Window Commands, The Echo Area, Printing Out Nodes, Miscellaneous Commands and Manipulating Variables.
info files are generated by the program, makeinfo, from a Texinfo source file. This manual describes version 1.64 of makeinfo. For more information on generating info files from makeinfo, see Making Info Files from Texinfo Files.
Texinfo source files use a documentation markup language designed to allow the same source file to generate either printed or online documentation. The Texinfo language is described in a separate manual, Texinfo: The GNU Documentation Format.