Hibernation is a power-saving state designed primarily for laptops. While sleep puts your work and settings in memory
and draws a small amount of power, hibernation puts your open documents and programs on your hard disk
, and then turns off your computer. Of all the power-saving states in Windows, hibernation uses the least amount of power. On a laptop, use hibernation when you know that you won't use your laptop for an extended period and won't have an opportunity to charge the battery during that time.