The handbrake is the brake you work with your hand to keep a parked car from rolling. In many older cars it is a lever between the front seats: you pull it up hard, and it holds the wheels still. In a lot of newer cars it is a small button or a pedal, but people still often call it the handbrake. British speakers say handbrake; American speakers more often say parking brake, and some people still say emergency brake — though actually you use it for parking far more than for real emergencies. You can use it as a verb too: to handbrake a car is to put that brake on. Drivers also talk about a handbrake turn, a sharp, showy turn that uses the handbrake to make the back of the car slide. That is not everyday parking.