The B on an automatic gear shift stands for Brake, a mode designed to help slow your car without relying entirely on the brake pedal. Common in hybrids, electric vehicles, and some CVT cars, it increases regenerative braking or engine braking to control speed. It’s especially useful when driving down long, steep hills, helping prevent your brakes from overheating and losing effectiveness. For everyday driving on flat roads and highways, stick to D (Drive) and use B when you need extra control on steep descents.