What is a UPS and How does it work?

An Uninterruptible Power Supply is a device connected between the power source and a computer to ensure that electrical flow is not interrupted. It is also called uninterruptible power source, UPS or battery/flywheel backup. UPS systems devices use batteries to keep the computer running for a period of time after a power failure. UPS systems cannot be confused with standby generators which do not provide protection from a momentary power interruption, or which may result in a momentary power interruption when it is switched into service, whether manually or automatically. UPS systems usually provide protection against power surges, brownouts and line noise as well.