What happens when your computer is in hibernate mode?

Hybrid Sleep mode is a combination of the Sleep and Hibernate modes meant for desktop computers. It puts any open documents and applications in memory and on your hard disk, and then puts your computer into a low-power state, allowing you to quickly wake the computer and resume your work.

I think hibernate is sort of like sleep mode. It puts your computer on low battery, but it's not turn off. And some unsaved information doesn't get erase.