ESP, or Electronic Stability Program, uses the brakes to brake individual wheels and keep the car going in the intended direction, when it detects that the vehicle is sliding out of control. It is often paired with TCS—Traction Control System (often controlled with the same button)—which cuts fuel to the engine when it detects wheel spin. Can’t lose traction when there’s no power going to the wheels.

In other words, it’s the fun button. Press it once when you want to have some fun, press and hold it to have a lot of fun (professional drivers only).