The anti-lock brake system keeps you from skidding -- skidding being the loss of traction between your tires and the road surface. The ABS pumps the brakes for you, which allows you to maintain steering control and prevents you from entering an uncontrolled spin. In a panic-braking situation, don't pump the brakes. Maintain steady pressure on the brake pedal and focus on steering.
When the ABS pumps the brakes, you may feel the brake pedal pulsing, you may hear a grinding or buzzing sound, or you may feel a vibration. These are not signals for you to release the brake pedal; in fact, they're indicators that the ABS is working. Maintain uninterrupted pressure on the brake pedal and let the ABS work for you.
The ABS can pump the brakes in much quicker succession than you could do manually and the system monitors traction so it can implement ABS braking when and where it is needed with much faster calculations than you can as the driver. If your vehicle has two-wheel ABS only, the ABS keeps the rear wheels from locking up. To maintain steering control, ease up -- don't pump, just ease up -- on the brake pedal enough to release the front wheels.
