Electrons are tiny particles that orbit the nucleus of an atom. Here is a drawing of atoms inside a piece of metal wire.

When enough electrical energy is added to the electrons–after flipping on a switch, or plugging in a cord, or adding a battery–they can escape from their normal orbit and flow along a path.

That's mostly how people use electricity . . . we make it flow along a path into things like light bulbs, refrigerators and CD players. The path electrons follow is called a circuit.