What do you have to do to make this system work? That's the best part: not a dang thing. If that little warning light in the dashboard didn't come on, you'd probably never know the system was ever springing into action.
When the road is slippery, for whatever reason, that little light is likely to come on. Rain-slick roads, icy patches and even wet leaves can come between the grippy rubber of the tires and the nubbly surface of the road. When a tire catches an icy patch or loses traction in a deep puddle, the sensors know it, and the traction control system kicks in.
It also helps when you're accelerating from a stop. While your car isn't moving very fast in those situations, having your wheels spin can still cause you to lose control. Best case scenario: You look like a fool on the local news with your tires spinning at a red light during your city's annual Snowpocalypse. Worst case scenario: You spin off the road and into a ditch.
When you've got traction in all four tires and they're spinning at the same rate, your car is far more stable. And that's why insurance companies often give discounts for cars with ABS and traction control. Insurers love stability.
Even older model cars had a rudimentary traction control system. Ever see an old, rear-wheel-drive muscle car peel out of a parking lot? If the rear end swayed and fishtailed all over the place while the tires squealed and smoked, that car probably didn't have a limited-slip rear differential. A limited-slip rear differential keeps the car's two rear wheels (where the engine's power is going) turning at the same speed. Limited-slip rear differentials are still used in powerful rear-wheel-drive sports cars, but traction control is a much more sophisticated system that's used in all types of cars. Mash the pedal of a car with a 600-horsepower, V-12 engine in 2013, and the traction control system will make sure as much power as possible is translated directly into moving the car forward, with little (or no) loss of power in a fancy fishtailing maneuver.