Because the Moon’s orbital and rotational periods are identical, it always appears to show the same face to the Earth and we never see its far side – the wrongly-called ‘dark side’. But in October 1959 the Russian satellite Luna 3 photographed the hidden terrain and the ‘Oxford globe’ reproduces details from that mission. However, because the entire lunar surface had not yet been mapped, portions of the globe have been left blank.
Pergamon Moon globe (Oxford, c. early 1960s)
To understand why observers from Earth only see one side of the Moon, see the animation below, which is explained on NASA's website (see 'External Links').