In the event of a blackout, power to your home or office is cut off and your lights and electronics will go out. Generally, the only things that survive the lack of electrons are components with built in batteries like your laptop or cell phone. But what about your desktop computer that you were just sitting on as you write that critical report?
An uninterrupted power supply (UPS) has a battery within its casing that powers any component connected to it in the event of a power loss. This can be a momentary loss (how many times have your office lights flickered and everything started randomly restarting?) or a full power outage. When the power goes out, the power immediately starts coming from the battery to power your components, which are generally the monitor and computer. No other components should be plugged into the UPS to preserve the usable power life of your UPS. The bigger the battery, the more time you have to safely shut down your computer and save your work. Remember though: if you have a high-powered gaming system, the computer will pull much more power and will need to be shut down much sooner than a standard work station, so be mindful of your computer type when you make your decision on Uninterrupted Power Supplies.