What is a Horsepower?

We have been using the term Horsepower (hp), quite very frequently to define the power of an automobile. But; what exactly is Horsepower? We found an extremely cool infographic in Jalopnik and sharing here for reference.  Let’s first got through the wikipedia definition – Horsepower (hp) is a unit of measurement of power, or the rate at which work is done, usually in reference to the output of engines or motors. The term was adopted in the late 18th century by Scottish engineer James Watt to compare the output of steam engines with the power of draft horses. It was later expanded to include the output power of other types of piston engines, as well as turbines, electric motors and other machinery.