ABS is Antilocking Breaking System. As the name implies this system avoids locking of wheels while breaking, which momentarily releases the breaking force and reappliies for effective breaking. These actions minimizes the chance of wheels getting locked and skidding of the vehicle. An imporatnt safety feature.

It is called the ABS(anti lock braking system). It is a safety feature for cars. The main benefit of this system is that the car does not skid when brake is applied suddenly even on wet surface. When you apply the brakes, it holds or locks the rim and after that whenevr the tyre is about to slip as it is held, the sensor senses it and releases the rim preventing the skidding of tyres(thats why it is called anti-lock). and this occurs many times in an anti-lock braking system in one single second. Great technology and very safe.

ABS is best explained here----- http://www.carwale.com/MyCarwale/Forums/ViewThread.aspx?thread=416&h=abs