A lever is a simple machine that consists of a rigid object, such as a board or beam, that is pivoted on a fixed point, known as a fulcrum. When a force is applied to the lever, it causes the object to rotate around the fulcrum. Levers are used to multiply force, change the direction of a force, or both.

In the case of a gate, the fulcrum is the hinge that the gate is attached to. When you push or pull on the gate, you are applying a force to the lever. This force causes the gate to rotate around the hinge, allowing you to open or close it.