Linux is a multiuser and multitasking system. The advantages of these features can be appreciated even on a stand-alone PC system. In text mode, there are six virtual consoles available. Switch between them using Alt-F1 to Alt-F6. The seventh console is reserved for X. More or fewer consoles can be assigned by modifying the file /etc/inittab.
To switch to a console from X without shutting it down, use Ctrl-Alt-F1 to Ctrl-Alt-F6. Alt-F7 then returns to X.