Traction control can be found in both standard and racing cars, and is there for the purpose of improving traction, though often with a loss of speed. In some countries (such as the United States of America), manufacturers aren't allowed to sell a new car not equipped with traction control.
Traction Control Systems by Engineering Explained
In this video, Jason Fenske explains how traction control works. This early Engineering Explained video was published on October 12th, 2011.
Some traction control systems use just the brakes to achieve the best traction levels, some reduce the engine's power to do so, and some use both.
Adjustable TSC
Some racing vehicles and high-end sports cars have adjustable traction control systems. These are adjustable from inside the vehicle while being driven, and are usually able to be turned off completely as well.