The "rear wheel" refers to the wheel located at the back of a vehicle, such as a bicycle, motorcycle, or car. It plays a crucial role in providing stability and support, as well as helping to propel the vehicle forward. In many designs, the rear wheel is responsible for transferring power from the engine or pedals to the ground. In bicycles, the rear wheel often contains the drivetrain components, including the gears and chain. This setup allows for efficient movement and speed control. In vehicles like cars, the rear wheels can also be part of a drivetrain system that includes features like differentials for better handling and traction.