A gearbox is a mechanical component that is used to transmit power from an engine or motor to another device, such as wheels on a vehicle. It does this by using gears which are designed to engage and disengage at specific points in order to control the speed and torque of the output shaft. Gearboxes come in many different types and sizes, depending on their intended use, but they all serve the same basic function: converting rotational motion into linear motion or vice versa.