ABS keeps the wheels from locking under heavy braking. Locked wheels can't steer, so ABS allows you to steer under heavy braking by modulating the brakes using a hydraulic pump, solenoid valves and wheel speed sensors.
The hardware (Sensors, Hydraulic Pump, etc)that does this can also do proportioning, traction control and stability control. Bosch ABS 5.3 has this in it's module. The Bosch system under discussion is also used in Caddies and Corvettes (from my recent reading)and utilizes all the features. From what I seen, the PCM must be programmed for these features to use them on the ABS module. I have ABS, Traction Control and EDB (Electronic Brake Distribution). CSVT's don't use the Traction control but I am not sure about the EBD.
