The Origins of Moons

You can tell a lot about where a moon came from based on what it's made out of and how it's orbiting. The reason you get moons around planets is the same reason you get planets around stars. You don't just get all the mass of the solar system collapsing into the sun. You get these little pockets that have enough gravity to form themselves together, then they're moving at high enough speed that they can resist falling into the Sun.