The full form of UPS is uninterrupted power supply or uninterruptible power supply (UPS). It contains a bettery in to supply power to the device when the main power source cut off from device.
The UPS in mainly used in offices and companies in computer when the power goes, it gives you the enough time to save your work and do your thing. When the power goes it switches to the battery in milliseconds to provide power to the load.
The battery in the uninterrupted power supply is relatively less but it is sufficient to save your work or properly shut down the deviceFor the safety purpose. It is a kind of continueal power system.
A UPS is mainly used in computer, day centers, telecommunications equipment where an unexpected power loss can cause serious damage and injuries that can lead to data loss and etc.
The run time of a UPS battery is relatively short in compared to some power supply batteries. But the main purpose of the UPS battery is to provide you the short time Power when the input power fails.
There are mainly two types of UPS available, first is
1. First is stand by power system that provide you the short term power when the input power supply shut off. These types of UPS are used in offices or in computers.
2. Second is online UPS which has its own inverter then gives you uninterrupted power supply.
It has two cons – first it is more costly then offline UPS, second it makes lot of noise as it has a cooling fan.
You can read more about UPS on Wikipedia