On a PRNDL selector, Neutral disengages the transmission from the engine and allows the vehicle to move independently of engine speed. In N, no normal drive force is transmitted to the wheels, so the car may roll if the brakes are released.
Neutral is useful when a vehicle must be stationary without selecting Park, and most automatic cars can be started in Neutral as well as Park. It is not the same as Park: Neutral does not engage the parking pawl that locks the transmission output shaft.
Drivers sometimes assume Neutral is harmless for coasting. Prolonged coasting at significant speed, particularly with the engine off, can damage some automatic transmissions because the lubrication pump may be driven from the transmission input side and stop operating when the engine stops.
Neutral also does not necessarily mean the engine is disconnected from every internal component. It describes the selected operating mode in which the transmission does not apply drive to the wheels. On a slope, the vehicle can roll, so the brake or parking brake remains essential.