Sleep is commonly known as Standby in Windows system. In Sleep mode, the power supply to non-essential and non-critical
component is withheld, and most system operation is shutdown and stopped. In Sleep mode, the power load reduce considerably, saving a lot of
energy. However, the power must not be cut off, and must be continue to
supply to the computer. Once out of power, the system will have to start
again just like a newly boot computer just started from power off
state.
On the other hand, Hibernate will save the data in physical memory to hard disk drive (HDD), and then power off the computer. When user wants to use the computer again, the computer will boot up and
load back the state at the last hibernation. The advantage of
Hibernation mode is that no power is wasted for maximum saving of power.
In Hibernation dormancy, no electricity is consumed by system. Beside,
restore from Hibernate is generally faster than computer reboot, and is
totally different from fresh start, as users can return to the exact
state of last hibernation with all programs running and documents opened
intact, instead of empty desktop.