One of the great things about the Mac is that it is built on top of UNIX. That means you can get a full UNIX terminal as needed for your more serious forays into geekdom. The one problem with the standard Mac terminal though is that you can't have tabs. If you need multiple windows, you have to open a separate window for each.

iTerm solves this problem by providing a terminal for the Mac that allows for tabbing... much like in Firefox. This makes a big different in cleaning up the desktop.