mc is a terminal mode filemanager, it is a program that runs in a terminal. Just start a terminal, and type mc,(then Enter), and it will run. Google for some tutorials on how to use it, but it is pretty self explanatory. It views, edits, and executes files as a start. I find it makes writing/debugging scripts easier, because you can quickly learn it, and it has hotkeys with many commands a linux system administrator would use.

It is an old program, but many people still swear by it, as it runs without an Xserver, and works over ssh. It is often compared to the old Norton Commander, the msdos filemanager program.