Watt is a unit used to measure power. It was named after James Watt, an inventor who made significant contributions to the development of steam engines in the 18th century. One watt is equal to one joule per second and represents the amount of energy consumed or produced by an electrical device over time. The term "watt" can also refer to a measure of power output, such as in the case of a light bulb that produces a certain number of watts of electricity.