Info
Info is a type of documentation. The documents are in a file format called texinfo, and can be read on the command line with the info program.
The Info ioslave allows you to read the info pages installed on your system, from within . You can use it very easily:

info:gcc

This would show you the top level node of the Info documentation for the compiler.
Info is a replacement for man, but is not widely used outside of software.
You can quite easily browse the info documentation you have installed from within the application, or you can use the info ioslave directly from within both and the mini-cli.