Astronaut: Person engaged in or trained for space flight.

Crater: A hole or depression. Most are roughly circular or oval in outline. 

Gravity: The force that attracts objects together.

Farside: The side of the Moon that never faces the Earth.

Lunar: Of or pertaining to the Moon.

Nearside: The side of the Moon that always faces Earth.

Orbit: The oval shaped pathway that the Moon takes around the Earth.

Revolution: The motion when an object goes around another.

Rotation: The motion when an object spins on its axis.

Spacecraft: Vehicle capable of traveling in outer space.