A UPS is a device to ensure supply of electricity to IT systems (computer etc) in case the mains electricity is cut off, to give the user time to back up work.
Uninterruptible Power Supply (UPS) is a...
Usually a SLA Battery (12 or 24 Volt) with Capacity depending on "up time" after loss of power and if it is an "online" or "offline" UPS. See Wikipedia