Why is there a dark side of the moon?

Well, darling, the moon doesn't have a "dark side" per se. The term we earthlings hastily coined is just a misnomer for the hemisphere of the moon that faces away from Earth. You see, both sides of the moon receive sunlight; it's just that we can only see one side from Earth. So, there's no dark secrets lurking on the moon's so-called "dark side," it's just moon business as usual.