I find mine particularly useful for checking whether the VSC light on the dashboard still works.
With the system switched on, you can supposedly do anything you want in the car and it will prevent you from crashing it. To test it out, I went for a spin down a nice twisty road and kept accelerating and completely let go of the steering wheel. When I came to a corner, the car started braking and turned round the bend as if it was on rails. Once round the other side, it accelerated back upto the speed I was going before. It was so good that I even managed to have a little sleep and the VSC system seemed to know exactly where I was going and I arrived safetly at my final destination.....the hospital.....in an ambulance
Seriously though, I think it just applies braking to a wheel if it detects it losing grip and modulates the throttle (eases it off a bit) until the slipping wheel regains some grip.