The copper atom has one lone electron in its outer shell, which can easily be pulled away from the atom.
When you receive a shock from static electricity, tiny particles called electrons actually move between your body and some other object.
In a nutshell, that's what electricity is -- the movement of electrons.
All matter is made of atoms, and all atoms have electrons.
Electrons occupy a space that surrounds the atoms nucleus. Each electron resides in a "shell," and each shell has a maximum number of electrons that it can hold.
For most atoms, the outermost shell does not contain its maximum number of electrons. Some atoms, such as copper, have only one electron in its outer shell.
Because there's only one electron in the copper atom's outer shell, it's not strongly attached to the atom. In other words, it is easily pulled away.
Electrons move from atom to atom in a wire, producing an electric current.
In a copper wire, electrons are able to move relatively freely from atom to atom.
Not all materials allow electrons to move so freely, however. Carbon, for instance, puts up a resistance to the flow of electrons. Electrons can still move through the carbon, it just takes more energy to get them to move.
You've no doubt heard the terms current and voltage.
Current describes how many electrons are passing through a wire or some other object at any given moment. High current means lots of electrons are in motion.
Voltage describes how much energy the electrons carry. High voltage means lots of energy.