UPS is an abbreviation for Uninterruptible Power Supply or Uninterruptible Power Source. That's a battery which is used to power some type of computer or a server to avoid the loss of information when the main power source fails for whatever reason or becomes unsafe. A diesel generator practically self-explanatory. UPSs and generators are used as a backup in data centers to back up the power supply and to ensure the uninterrupted running of all the servers located there. Due to the fact that the UPS runs at all times, it provides the necessary power for the web servers to remain functioning until the generator starts and takes over. Using this sort of a backup is essential for any data center or hosting company that wants to keep their hardware and info intact in case there is a power surge or outage, since it offers them lots of time to react until the issue is resolved and the main power supply is restored.