When a computer hibernates, usually simply by pushing the on/off button, it takes a few seconds for it to get to a state of electrical rest. By pushing it again, it comes back right away to the same state it was in prior to this change, that is to say the same desktop environment (windows, programs and files in use).
If working with Windows, you can find out how to get your computer to hibernate in the power options, in the Control Panel.
If you use Linux and your distribution doesn't have it by default, look for more information online. There are more websites with information: here and here...