A Cycler is a station which is placed on an orbit that repeatedly encounters 2 bodies and provides living facilities which can be used while in transit. The idea is that the mass heavy living facilities don't need to be accelerated and decelerated every time a spacecraft makes the journey, just dock to it, chill out for a week, or maybe even months. Then leave when you get to the target, similarly the return journey involved a rendezvous and docking. This particular design's orbits are far from ideal, and lead to inefficient maneuvers, in part because of the large munar SOI I have to avoid encounters and in part because the distances are so short.