One of the simplest and oldest gadgets in the world is the lever. Any rod or stick can act as a lever, helping to move heavy objects or prise things apart. Leavers are also used for lifting, cutting, and squashing. The action of a lever can make a push more forceful, or make it a smaller push. It can make a push more forceful, or make it a smaller push. It can also change the direction of a push. The difference between the sizes of the push you make on a lever (the effort) and the push the lever itself makes (the load) is called mechanical advantage.
A lever on a central pivot can also be used as a balance. The lever balances if the effect of the force (push) on one side of the pivot is the same as the effect of the force on the other. A seesaw is one sort of balancing lever. It is a plank balanced on a central post or pivot. A big person can balance someone small and light if they sit nearer to the central pivot of the seesaw.
How a lever works
A lever tilts on a pivot, which is nearer to the end of the lever with the load on it. The effort, or force, is the push you make on the long end of the lever to lift the weight of the load.
Ruler, book, pivot (box).
Pivot, plank of wood (seesaw).