What RNG mean ?
Random Number Generator. Pretty much any game you play at all will have it dictating some certain aspects, such as where enemies spawn, the patterns of their movements and when they attack, item spawns, even damage and healing ranges. The most infamous examples would be in RPGs and life simulators such as Animal Crossing and The Sims. Also GTA with random helicopter crashes and traffic/police mishaps. I guess you could call it the game mechanic equivalent of luck.
