The Lunar Orbital Platform-Gateway (LOP-G) is a proposed lunar space station. The goal is to get humans and technology a little deeper into space to pave the way for human-crewed missions to Mars and near-Earth asteroids. The LOP-G will even serve as the staging point for Mars-bound spacecraft.
NASA is going to great lengths to build this platform near the moon, so why not build it on the moon? The lunar surface contains the material for radiation sheilding and possibly propellant. The moon could become a spacecraft parking lot and fuel station for lunar explorers and Mars transport spacecraft without the complexing of space docking. Plus, it's a great place to try out a Mars surface habitat.
Buzz Aldrin thought the LOP-G proposal is absurd and said:
Why would you want to send a crew to an intermediate point in space, pick up a lander there and go down?
I have great respect for the brilliant people at NASA. There must be a reason why they want to do the LOP-G as proposed.