Traction control is a vehicle-safety feature that is designed to help a car make the most out of the traction available on a road with low friction. When a car without traction control accelerates on a slippery surface, for instance, the roads with loose gravels, or roads covered with ice, the wheels tend to slip. Traction control helps the driver to make the most out of the little bit of traction available on such slippery surfaces.
New 4WD cars come with advanced traction control. Whether or not you should leave traction control ON or OFF, depends entirely on the surface or terrain you are driving on. Sometimes it’s better to turn traction control ON, while at other times, it isn’t really a good idea. With the traction control off, the wheels with the least traction get most of the torque and this makes the wheels spin. The spinning wheels make the car go nowhere. When the traction control feature is turned on, the car brakes the spinning wheels, this allows more torque to be directed towards other wheels of the car (with traction).
Therefore, it is a good idea to leave traction control ON, especially if you are climbing up a hill with loose gravels. In situations where you are in a muddy road or a river crossing, it’s better to leave traction control OFF, in order to allow continuous momentum of the wheels.