The moon rotates on its axis proportionally with the rotation of the Earth, so we only ever see one side of it and the far side is in perpetual darkness.
THE REALITY
In fact, that’s mostly true. The moon does indeed spin in proportion with our planet so that we can only ever see exactly the same side of it from Earth.
The Sun, however, lights up the bit we can’t see as often as the near side of the moon. During a solar eclipse in particular, the far side gets completely illuminated while the near side to Earth is plunged into darkness.
Why Do We Only See One Side of the Moon?
What’s on the Far Side of the Moon?
Why can’t you see the far side of the Moon?