The axle is connected to the frame via the suspension, with wheels installed at both ends. Its function is to transmit forces and moments in all directions between the frame (or unitary body) and the wheels. Based on function, it can be categorized into steering axles, drive axles, steering drive axles, and support axles. The differential housing in the middle of the axle is used to change the direction of power transmission, reduce speed, and increase torque, while structures such as the wheel hubs on both sides are responsible for mounting the wheels and transmitting power, making it an important component of the automotive driving system.