Is a state of inactivity to save energy. In computing this expression is used for powering down a computer while preserving the state it is in. The content of the RAM (Random Access Memory) is saved to a drive (usually the main hard disk of the system) and will be restored in RAM as soon as the system is brought back out of hibernation. Not to be confused with sleep mode, which is another energy saving method that uses a little energy to keep the data in RAM. The advantage of sleep mode is that the system is ready for use almost instantaneously where waking from hibernation takes some time.