All vehicles need to have tail lights and brake lights. Tail lights are the rear lights that run when your headlights are on. They serve as beacons showing other drivers that you are on the road.  Brake lights only illuminate when you step on the brakes. These lights warn drivers that you are slowing and coming to a stop. The brake lights and tail lights are often in the same housing, with brake lights being brighter than the tail lights. New vehicles also have a separate brake light that is higher up on the vehicle than the tail lights.