A taillight is a red light located at the rear of a vehicle, designed to signal the presence and actions of the vehicle to others on the road. It typically illuminates when the vehicle's headlights are on and becomes brighter when the brakes are applied, alerting drivers behind to the vehicle's slowing or stopping. Taillights are essential for road safety, especially during low visibility conditions like night or bad weather. They are part of a vehicle's lighting system, which also includes headlights, turn signals, and hazard lights, all of which work together to ensure safe driving and communication between vehicles.