hiberfil.sys??

[Zarick]

What is hiberfil.sys
Im trying to defragment my drive and it says this file cannot be moved.
Can someone tell me what it is?

 

[AndyHui]

When Windows hibernates, it dumps the entire contents of RAM into the file. This file is then read when the computer is brought out of hibernation, so that you can resume your Windows session from the same place where you left off.