Anti-Lock brakes maintain traction over slippery terrain. At it's most basic the computer detects losses of traction to the wheels. Then it "pumps" the brakes. Depending on when you took Driver's Ed you might remember being told to pump the brakes if you are skidding or in danger of a spinout. This is component takes this important action, which can easily be forgotten in the chaos of the road, and automates it for driver safety. It's important to realize this will only rarely reduce braking distance but it will increase driver control.