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That's the tire pressure monitor system light. It has come on because there is a tire with low pressure, a problem with one of the pressure sensors, etc.
The first thing you'll need to do is make sure all tires are properly inflated. By far the most common cause of the light coming on is because there is a low tire and most likely you have at least one that is low.
If the tires are properly inflated, or if correctly inflating them doesn't turn the light off, then there is a deeper problem in the system. The next most common cause would be a bad pressure sensor. A scan tool would be needed to diagnose it further.