Gears and their mechanical characteristics are widely employed throughout industry to transmit motion and power in a variety of mechanical devices, such as clocks, instrumentation, and equipment, and to reduce or increase speed and torque in a variety of motorized devices, including automobiles, motorcycles, and machines.

They are found in the mechanisms of cars, trucks, bikes, pumps, analog watches, wind turbines, bull dozers and most engineering machines.

Gears are used for transmitting power from one part of a machine to another. In a bicycle, for example, it's gears (with the help of a chain) that take power from the pedals to the back wheel.