UPS is an abbreviation for Uninterruptible Power Supply or Uninterruptible Power Source. It's a battery used to power a personal computer or a hosting server to avoid the loss of information in case the main source of energy fails for reasons unknown or becomes risky. A diesel generator basically self-explanatory. UPSs and generators are widely-used as a backup in data centers to back up the power and to ensure the consistent functioning of all of the web servers located there. Since the UPS operates at all times, it provides the required power for the servers to remain up and running until the generator starts and takes over. Using this kind of a backup is crucial for any data center or hosting company that wants to keep their hardware and data intact in case there is a power surge or outage, since it provides them with enough time to react until the issue is resolved and the main power supply is restored.