Why can we only see one side of the Moon?

On Earth we only see one side of the moon because the Moon and the Earth are tidally locked and the Moon is in a state of synchronous rotation. This means that the Moon's rotational period, the time it takes to make one full rotation, is the same as its orbital period, the time it takes to orbit the Earth. So as the moon orbits the Earth it is also rotating the exact amount to keep one side facing Earth at all times.