Uses
Hibernation saves electrical power. After hibernating, the hardware is completely powered down (just like for a regular shutdown). Therefore a hibernated machine uses no more electrical power than one which is switched off. Meanwhile, hibernation is a means of avoiding the burden of saving unsaved data before shutting down and restoring all running programs after powering back on.
Hibernation is used in laptops, which have limited battery power available. It can be set to happen automatically on a low battery alarm. Most desktops also support hibernation, mainly as a general energy saving measure.
Read more about this topic: Hibernation (computing)