He used it to compare the power of steam engines to the power of horses. Today the term is used to measure the power of devices such as automobile engines, gas turbine engines, electric motors, and nuclear power plants.
Power is a measure of the rate of doing work.
The amount of work to move one pound a distance of one foot is one foot-pound. The watt is the unit for measuring power in the metric system. One horsepower equals 745.7 watts. The power of an engine can be defined in several ways. Indicated horsepower measures the power produced inside the cylinders of an engine.