For 90% of the time, don't touch the button. By default when you turn the car on, DSC (Dynamic Stability control + Traction control) is fully on. When the system is on, no lights come on the dash. When the system is actively working, the symbol flashes.

In deep snow, sand, and/or if you feel like doing some enthusiastic driving, push the DSC button which shuts DSC off. The light will come and stay on the instrument cluster, meaning it is off. The system is in reduced function, with only Traction control, so larger slip angles are permitted.

If you hold the DSC button for about 3-4 seconds, this shuts DSC and Traction fully off. If you really feel like being naughty (or if you're auto-x'ing), this is the mode to be in.

Do a search on this forum.