Luna is major satellite of the planet Earth in the Sol System. Unlike most satellites, it is comparably large when compared to the planet it orbits creating a system that’s almost a binary planet.
Also, as the satellite of the human homeworld, it was the first body reached and colonized by that race, first in 1969 by Neil Armstrong.
It is the homeworld of the Lunites, descended from 22nd Century Specialists who were liberated and given the ability to reproduce and live longer lives.