It's a game like Gmod's Murder or TTT gamemode, Town of Salem, or Whodunit/Who Done It, but it's in space, so it's actually more like Space Station 13, but it's more fun and easier to get into and learn (so i've heard)
Basically, there's a team of crewmates who have carious tasks to complete around a spaceship, and then there's the imposter who tries to blend in with the crewmates while also killing them without being figured out and ejected into space