The Turn Off Computer dialog box

3. Choose one of the following options (as available):
Hibernate: Saves everything on the screen and puts the computer into a minimal
power-consumption state. When you restart the computer, the desktop will look
exactly as you left it (hopefully).
Standby (if available): Puts the computer into a minimal power-consumption
state, but does not save current settings. Restart will be quicker than if you had
turned off. But you’ll be returned to an empty desktop.
Turn Off: Turns the computer all the way off. Nothing is saved, no power is
consumed while the computer is off, and restarting will be from scratch. (The
computer will go through the POST again at restart.)
Restart: Briefly shuts off the computer, and then instantly restarts it. Also known
as rebooting. Required after certain kinds of hardware and software installations,
and also after a serious “crash” when something has caused your computer to
start acting weird.
Your computer might show additional instructions at this point. Most likely, however, the computer will
just shut down (or go to sleep.) Note that if you selected Turn Off, chances are your computer will
indeed shut itself off. So you don’t need to press the Power button on the system unit to finish the job.
However, some older computers don’t have this capability, in which case you will need to press the
main Power button to complete the shutdown procedure. As a safety device, to prevent accidental
shutdown, some computers require that you press the Power button and hold it there for four or five
seconds before the computer actually shuts down.