A differential gear is a mechanical device used in vehicles to allow the wheels to rotate at different speeds, especially when turning. This is important because the outer wheels travel a longer distance than the inner wheels during a turn. The differential gear helps distribute engine power to the wheels while accommodating this difference in speed. Typically found in the drivetrain of vehicles, the differential gear consists of a set of gears that work together to achieve this function. It is commonly used in various types of vehicles, including cars, trucks, and motorcycles, enhancing stability and control while driving.