TunaFish and Retric gave great explanations, but I want to add a quick conceptual point: the moon (and the Earth) is falling into the sun. Constantly. It's just

TunaFish and Retric gave great explanations, but I want to add a quick conceptual point: the moon (and the Earth) is falling into the sun. Constantly. It's just that the moon (and the Earth, and the other planets) have so much velocity tangential to the direction of the sun that instead of falling into the sun, they fall around the sun. That's what an orbit is.