A movable pulley is a pulley that can freely move. This is only one of three types, the other two being fixed and compound pulleys. Examples of movable pulleys are elevators.
A pulley is a device made up of a wheel and an axle, and is used to lift heavy objects more easily. A rope, cable or chain passes through the circumference of the wheel, allowing the cable or belt to move and change direction. When comparing a movable pulley with a fixed one, it is better to use the movable pulley, as it has the mechanical advantage of two ropes. To further increase this mechanical advantage, a combination of fixed and movable pulleys is utilized, resulting in a compound pulley.