The Moon Has A Far Side, Not A Dark Side
No one side of the moon is permanently dark. As the moon orbits the Earth, its illuminated and shadowy sides switch, depending on which side is facing the sun. The far side of the moon is often referred to as the dark side, however, because humans had never seen it until the invention of 20th century spacecrafts. Although the moon rotates, it does so at roughly the same speed as it orbits Earth. This means that we don't observe it spinning, and instead only view what we call the near side of the moon.
from Universe Today
Key Facts In This Video
The Soviet Luna 3 probe was the first spacecraft to image the far side of the moon in 1959. (0:42)
The far side of the moon looks dramatically different from the near side. (1:22)
Some deep craters on the moon could hold reserves of ice. (2:32)