UPS is an abbreviation for Uninterruptible Power Supply or Uninterruptible Power Source. That's a battery used to power some type of computer or a web server in order to avoid the loss of info in case the main source of energy fails for reasons unknown or becomes risky. A diesel generator is more or less self-explanatory. UPSs and generators are used as a backup in data centers to back up the main power source and to guarantee the consistent functioning of all the machines located there. As the UPS operates all the time, it offers the necessary 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 hosting company that wants to keep their hardware and info intact in case there is a power surge or outage, as it gives them ample time to react until the issue is resolved and the main power supply is restored.