What is Copper?
Diagram of a copper atom
Copper is a kind of atom that has only one electron in the outermost ring. Copper is a fairly heavy atom, that can only be made inside a red giant star. When the red giant star has finished making copper and moved on to heavier kinds of atoms, eventually it explodes into a supernova and shoots out the copper atoms along with lots of other kinds of atoms.
All of the copper in the universe comes from this process. Copper came to Earth when the Earth first formed out of a nebula cloud. All animals and most plants need copper in order to make some of their enzymes.
Because copper atoms have only one electron in their outer shell, like silver and gold, it's a kind of metal, and it's very easy for copper to share electrons with other atoms to make bigger molecules. Copper atoms can combine with each other to make pure copper, or they can combine with oxygen to make copper oxide (like rust, only with copper instead of iron).
Copper makes it particularly easy for electrons to move from one atom to the next, and that makes copper a good metal for moving electricity from one place to another. We use copper wire inside electric cords to move electricity from the wall to your computer, and inside telephone cords to move electricity from your land-line telephone to your friend's telephone to carry the sound of your voice.