A pulley is a simple machine that helps lift heavy objects with less effort. It consists of a wheel on an axle, with a rope or cable that runs over the wheel. When you pull down on one side of the rope, the other side lifts the load. This makes it easier to move things like boxes or furniture. Pulleys can be used alone or in combination to create a pulley system. For example, a block and tackle system uses multiple pulleys to reduce the amount of force needed to lift a heavy object. This is especially useful in construction or when using cranes.