This is a misconception. Both sides of the moon are actually lit by the Sun. However, due to the Moon's synchronous rotation (which means that the same side of the Moon always faces Earth), we can only see one side of the Moon from Earth. The side of the Moon facing away from Earth is referred to as the "far side" or the "dark side" of the Moon, but it is not perpetually dark. Like the side of the Moon that faces Earth, it experiences day and night cycles as it rotates on its axis. The term "dark side of the Moon" is a misnomer and refers more to the fact that this side of the Moon is permanently turned away from Earth rather than being in perpetual darkness.