UPS is an abbreviation for Uninterruptible Power Supply or Uninterruptible Power Source. It is a battery which is used to power a personal computer or a web server to avoid the loss of info in case the main power supply fails for reasons unknown or becomes unstable. A diesel generator is more or less self-explanatory. UPSs and generators are used as a backup in data centers to back up the power and to ensure the consistent running of all the servers located there. Since the UPS runs constantly, it provides the required power for the servers to remain operational until the generator starts and takes over. Using this type of a backup is a must for any data center or web hosting provider that wants to keep their hardware and information intact in the case of a power surge or outage, due to the fact that it offers them plenty of time to react until the issue is resolved and the primary power supply is restored.