Logging off means that you are no longer on the computer, but the computer is still turned on. Before turning the computer off at the power switch, you should run the shutdown procedure, so that Windows has a chance to sort itself out, save changes, quit open programs, and close connections to other computers.
You can shut down by pressing Ctrl+Alt+Delete (to summon the Windows Security dialog box) and then clicking the Shutdown button. Or you can choose Start→Shut Down. Either way, the Shut Down Windows dialog box (Figure 2-1) appears on your screen.
Figure 2-1. Click the drop-down list button for the shutdown choices. Choose Shut Down to turn the computer off, or Restart to exit Windows and then restart Windows without turning the computer off. You can add "Stand by" and "Hibernate" options, if your PC offers them, using the Power Options control panel (see Section 8.17.2). (These commands are primarily used on laptops.)
If other people on the network require access to files or folders that you've shared on your machine, log off instead of shutting down. That way, your PC's shared files remain available to others on the network, but the machine is still safe from inspection by somebody who sits down at your desk while you're away.
The drop-down menu offers these options:
Log Off [Your Name] leaves the computer on, awaiting the next person who logs on.
Shut Down quits ...