What is the round yellow warning light on your 2001 vw jetta mean?

My best guess is its your Traction Control Warning... Meaning your Tires are lossing traction to the road either because of snow ice or water. the reason that is what i think it is, is because a friend of mine has a Mercedes with a large triangle warning light (Yellow) that means the same thing. Again its not a professional opinion its just what i think it might mean