As a matter of fact, it's all dark. But seriously, the "dark side" of the moon is the side we can never see from earth. It isn't literally dark so much as just

As a matter of fact, it's all dark. But seriously, the "dark side" of the moon is the side we can never see from earth. It isn't literally dark so much as just unseen. Consider similar usages like "dark energy" or "a shot in the dark".