go is a small shell command for changing directories quickly. Typically you have a set of directories that you work in. Typing out the names of those dirs in full can be tedious. go allows you to give a shortcut name for a directory -- say ko for D:\trentm\main\Apps\Komodo-devel -- and do the following:

C:\> go ko
D:\trentm\main\Apps\Komodo-devel>

and

C:\> go ko/test
D:\trentm\main\Apps\Komodo-devel\test>

These examples are from Windows (in the cmd.exe shell), but go works for Linux, Mac, etc. as well.

Think of it as a super cd. See GettingStarted for more details.