On many modern vehicles, the wheel bearing is not a loose part you pack with grease - it is built into a sealed unit called a hub bearing assembly. Here is what a wheel hub and bearing assembly is.
An all-in-one unit
A hub assembly combines the wheel hub (where the wheel bolts on), the bearing, the mounting flange, and often the ABS sensor ring into a single sealed, pre-greased unit. It bolts to the steering knuckle as one piece; see pressed-in vs bolt-on.
Why makers use it
Because it is sealed and preset at the factory, a hub assembly is precise, low-maintenance, and easy to replace - no packing grease or setting preload by feel. It also neatly carries the wheel-speed sensor for ABS; see how ABS works.
When it fails
The whole unit is replaced when the bearing wears - it cannot be repacked; see signs of a bad hub bearing. Symptoms are the usual humming, play, and sometimes an ABS light.
Replacing it
Unbolt the old assembly, clean the knuckle, bolt on the new one, and torque the axle nut and bolts to spec; see hub torque. Do both sides on high-mileage vehicles. Keep the brakes fresh with quality pads and hardware.