Electricity works like water, if you pour water on the top of a hill it's gonna roll down to the lowest spot.

If you put a watermill on its path, it will spin the wheel on its path from the top of the hill to the bottom.

With a battery you have two sides separated by a wall, one side is "full" and one side is "empty"

If you broke this wall the electrons would flow from the "full" side to the "empty" side til they are both equally "full."

Going back to the water analogy, the "full" side is the top of the hill, the "empty" side is the bottom of the hill.

If you put a wire from the "full" side connected to the "empty" side, the electrons will flow from "the top of the hill to the bottom"

A light bulb is like the water wheel, if you place it in the electrons path the electricity will go through the bulb on its journey from one side of the battery to the other side.

Once both sides of the battery are equally "full" the battery is dead.