Here's why:
* Tidal Locking: The Moon is tidally locked to Earth, meaning the same side always faces us. This happens because the Moon's rotation period is the same as its orbital period around Earth.
* Both Sides Are Visible: While we only see one side from Earth, the entire surface of the Moon has been photographed and mapped by spacecraft orbiting it.
So, what people often refer to as the "dark side" is actually the far side of the Moon. It's not actually dark, but rather the side that faces away from Earth.
The far side of the Moon has a different appearance than the near side, with fewer maria (dark, smooth plains) and more craters. This difference is due to the different geological history of the two sides.
