Graphite is a form of carbon where the atoms join together in flat rings that slip over each other easily. It is one form of pure carbon. Another is diamond where the atoms are all attached to each other in a much stronger way – you can't wipe bits of diamond off a diamond ring with a piece of paper. Graphite's flakey structure also helps it to be a good lubricant at very high temperatures. Different grades of graphite have different sized flakes.