Pg 142 owners manual. Brake indicator monitoring system. Could be anything from low fluid to more serious problem. If your not mechanically inclined or little knowledge of auto maint/repair have a mech check it out. You can also access the onboard OBDll by turning key forward 3 x's(do not start vehicle) on 3 rd time leave forward and a code will appear in mileage window. these codes will give you a diagnostic that can be looked up and solution found.
You can get an exclamation mark on your 2008 Dodge Caravan if you have a low tire pressure sensor. The best thing is to get the sign identified by a professional so they can be able to fix the problem immediately.