The first mission to land on the Moon was Apollo 11. Its orbit was calculated using the laws of celestial mechanics. After escaping Earth's gravity the much weaker gravity of the Moon was used. It was also the first time man had landed on the Moon. Armstrong made the first steps on the Moon on 21 July at 2h 56min 20s UT.
The lunar landscape is composed of rocks of all sizes and of dust, as had been predicted by observations from the Earth. The areas called "seas" are actually plains. Apollo 11 landed on one of the seas, the Sea of Tranquillity, for safety reasons. During subsequent missions, landing sites were chosen in more rugged regions.