Transmission Gear is a mechanical device used in motor vehicles to transfer power from the engine to the drivetrain. It is composed of a set of gears that are connected to the engine and the drivetrain, allowing the engine to rotate the drivetrain at different speeds. The gear ratio determines the speed of the vehicle, and the LOW gear is the lowest gear ratio available. LOW gear is used for starting the vehicle, climbing hills, and driving in LOW-speed situations.