What is the difference between normal braking system and anti-lock braking system?

The normal braking system includes the use of braking shoes for the drum brakes and the disc arrangement for the disc brakes, which has to be manually managed by the rider. In abrupt braking, the tires are mostly locked and skidding of the bikes on uneven roads can cause accidents. ABS manages the brakes, by not locking up the tires and holding & relieving the disc with the calipers. This leads to lesser chances of accident of wet and uneven roads.