The "B" gear in a Toyota Corolla is a gear shift position that favors lower gears. It is also known as the engine braking or brake gear in an automatic transmission system. When the driver releases the accelerator pedal, the B gear helps to slow down the vehicle by downshifting to a lower gear, which increases the engines RPM and provides more resistance to the wheels. The B gear is useful when driving down a steep incline or when decelerating. It is important to note that the B gear should not be used for normal driving conditions, as it can cause unnecessary wear and tear on the transmission system.