If you step on the brake of a car while driving, the frictional force between the tires of the car and the surface of the road increases in opposition to the motion of the car. Consequently, the car slows down.
If you release your foot from the brake pedal when the car is still at half speed, the frictional force reduces and the car speeds up a bit even without pressing the throttle. Eventually, the frictional force will slow down and stop the car if the throttle is not pressed.
