The terms ‘sleep’ and ‘hibernate’ used in the tech sense aren’t really self-explanatory so you may be forgiven for not actually knowing what is going on when you put your PC or laptop into one of these states. Many notebook computers enter sleep mode automatically when left idle for a defined amount of time.
Put simply, when you’re PC or laptop goes to sleep it is storing all the data about the programs you have running etc into it’s memory (RAM) and then shutting off all the peripherals connected to it (screen, hard drive, CD/DVD drive, possibly USB ports etc), the computer its self is still powered on but is running in a very-low powered state. This is good if you are running a laptop and you need to step away for a few minutes, it conserves battery power. The advantage of using sleep over hibernate is that when you wake the computer (by moving the mouse or pressing a key on the keyboard) it is much faster to recover back to where you left off.
When the computer is sent into hibernate mode, all your data is stored in memory (RAM) but the computer actually powers completely off. This can be handy if you want to come back to what you were working on a few hours or days later. It obviously saves a lot more power/battery charge than sleep mode but it isn’t as quick to reboot and reload your data as compared to sleep.
I hope this has helped someone out there. I have tried to keep it as simple and easy to understand as possible!