What is wheel hub assembly?[From Wikipedia]

A wheel hub assembly (WHA), also referred to as hub assembly, wheel hub unit, wheel hub bearing, etc., is an automotive part used in most cars, passenger vehicles and light and heavy trucks.

It is located between the brake drums or discs and the drive axle. On the axle side, it is mounted to the holding bracket from the chassis; on the disc side, the wheel is mounted to the bolts of the WHA. When replacing, a wheel hub assembly should be torqued to the vehicle's specifications to prevent failure.