ESP is a further enhancement to the anti-lock braking system (ABS) and traction control system (TCS). The ESP is designed to detect a difference between the driver's control inputs and the actual response of the vehicle. When differences are detected, the system intervenes by providing braking forces to the appropriate wheels to correct the path of the vehicle. This automatic reaction is engineered for improved vehicle stability, particularly during severe cornering and on low-friction road surfaces, by helping to reduce over-steering and under-steering.
GF: What's this ESP button in my car?
BF: A function to help you not drive off the road on messy weather, hit it.