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You are mixing up Hibernate with Suspend/Standby.
Hibernation takes all the data that is in memory, and writes it to the hard drive, then switches off the power completely. You then turn the power back on, and it will resume Windows to where it was previously.
Standby/Suspend will just turn off most devices, but keep power to memory, to hold the data. If you lose power to the memory, then all the data will be gone, and you will have to load Windows fresh again. With Hibernate, you can unplug the power and the next time you plug power back in it will still be fine