What is the difference between an inverter and a UPS?

An inverter is a device that converts DC (Direct Current) power into AC (Alternating Current) power. For example, a 12V inverter will convert battery power available at 12V DC into AC power at 230V in India.

UPS (Uninterrupted Power Supply) is a device that normally provides back-up power supply for any electrical gadget. To do this, the UPS typically includes the inverter, battery and battery charger in one standalone unit. UPS units also provide protection against many electrical problems like over-voltages, brownouts, power surges etc. and in certain cases also communicate with the equipments they are powering.

We often use the terms interchangeably in India, as given our need for back-up power, a standalone inverter (that converts only DC power to AC power) is often not very useful and we invariably need a device that is also equipped with a battery charger and hence, a UPS.