Everything in the universe is made of atoms, and atoms are made of electricity. Atoms are made of even smaller particles called protons, neutrons, and electrons. The protons and neutrons (NOO-trons) are packed tightly together in the middle of the atom, and we call them the nucleus (NOO-klee-uss) of the atom. Around the nucleus there are electrons, orbiting around and around the nucleus kind of the way that the earth goes around the sun. There's empty space between the electrons, so an atom is mainly empty space.
Protons and electrons have electrical charges. Protons have a positive charge, and electrons have a negative charge (neutrons don't have any charge). Because electrons and protons have opposite charges, the electrons and protons tend to move toward each other, just the way the negative end of one magnet will tend to move toward the positive end of another magnet. But because the electrons have a lot of forward momentum, the electrons don't just crash into the nucleus. The electrons have to keep moving forward, and the combination of moving forward and moving towards the middle keeps the electrons going around and around the nucleus of the atom. Sometimes an electron does escape from its atom and runs off to join another atom. That's a little tiny bit of electricity. Electricity is electrons that have gotten loose from their atom.
Moving electricity through a circuit
Some kinds of atoms lose their electrons more easily than others. It depends on whether the outer shell of electrons is full or not. For example, copper atoms have only one electron in the outer shell. That's very unstable, and it's easy for copper atoms to lose that electron. We call these kinds of unstable atoms metals.
Electricity is all throughout space, because of the loose electrons in space. There are electrons inside stars, and on all planets. Lightning is just one form of natural electricity. When life first got started on Earth, electricity probably had something to do with it. And inside your body, your thoughts are really little spurts of electricity that travel along your nerves and between cells in your brain. When a person has a seizure, that is when too much natural electricity gets loose in their brain.
In the last two hundred years, people have learned to use electricity for their own purposes, to run machines. When we want to move electricity around (like through a cord to your computer), we make a long wire of copper atoms, because electrons move easily from one copper atom to another. When we want to keep electricity from moving (like out of the cord and onto your hand, where it would give you a shock), we make a wrapper out of rubber or plastic, because electrons don't move easily through those materials. We use electricity to heat our houses, light up dark rooms, cook food, run washing machines, and listen to music. Some people use electricity to run their car!