Hibernation is a power-saving state used by computers in which the contents of the system's RAM are saved to the hard disk before the computer powers off completely. When the system is powered back on, the saved memory is restored, allowing users to resume their previous session exactly where they left off. In cybersecurity, hibernation can pose risks because sensitive data stored in RAM, such as passwords or encryption keys, may be written to disk in an unencrypted form, making it potentially accessible to attackers if the disk is compromised. Proper security measures, like disk encryption, are recommended to mitigate these risks.