ABS stands for Anti-Lock Braking System. It solves the problem of wheels stopping rotating when the brakes are applied hard, such as in an emergency situation, or when roads are wet. A computer monitors the speed the wheels are rotating at, and when it senses one is locking up, it pulses the brakes on and off, keeping the wheel slowing but not stopping. The effectiveness of the system is often derided by idiots, who never brake hard enough to activate the system, or when they do, back off because the pedal starts vibrating to indicate the system is working. Probably due to ignorance connected to not reading the owner's manual.