The driveshaft is a spinning tube that is responsible for passing along power and torque to the driven wheels. In this case, we're mainly talking about the rear-wheel drive or all-wheel drive cars. Thereby, the driveshaft's long reach allows the engine and transmission to effectively send power to the rear. In the case of front-wheel drive, they have the half-shaft to manage the same thing... Send power to the driven wheels. Since the engine and driven wheels are both in the front, there's no need for a full-sized driveshaft. Hence, why it's called a half-shaft, as it's significantly shorter. Its role is to extend from the transaxle and front differential to the front wheels.