ABS (Anti-lock Brake System) prevents the wheels lockup and allows the driver to retain steering capabilities during the braking.
It must be mentioned that this feature is provided by reducing the braking force when the slip ratio reaches a certain value.
This means that in this condition the braking capability of the car decreases although the wheels will not lock and the car can steer.
As in case of the Traction Control set-up, you can choose one of the default set-up: 0% (no ABS assistance), 100% (ABS assistance at full potential), or a pre-set value (edit your own ABS values or play with the ABS set-up from the EDIT page).