Sleep is a power-saving state, or mode. Sleep saves all open
documents and programs, and allows the computer to quickly
resume full-power operation (typically within several seconds)
when you want to start working again.
Use shut down only when you must turn off the power to your
computer, for example, when you want to add memory or you
don't plan to use the computer for several days.
Ending a Program That is not Responding
Standby is a state in which the display and hard disks turn off, so
that your computer uses less power. When you want to use the
computer again, it comes out of standby quickly, and your desktop
is restored exactly as you left it. Because standby does not save
your desktop state to disk, a power failure while on standby can
cause a loss of unsaved information.
Hibernation is a state in which your computer shuts down to save
power but first saves everything in memory on your hard disk.
When you restart the computer, your desktop is restored exactly
as you left it. Use hibernation to save power when you will be away
from the computer for an extended time while working.
Use shut down when you must turn off the power to your
computer. This action shuts down Windows so that you can safely
turn off the computer power.
Shutting Down Your Computer