Using the console
From LXF Wiki
The console is the text-based interface to Linux. Many servers don't run the X Window System GUI, so users administer those machines at the console (or via a remote login). You can switch to the console by pressing Ctrl+Alt+F2 (or another F key) while you're in the GUI; then you can log in and enter commands as described in the Basic Bash guide.
Linux supports virtual terminals, which means you can have multiple logins at the console. When you've switched to a console, try pressing Alt and the left and right cursor keys -- you can then open up an email client in one terminal, while editing files in another. To switch back to the GUI, press Ctrl+Alt+F7 (may be F5 or different on some distros).