What does "RNG" mean?

RNG=random number generator. It refers to the simple concept that if your character has 60% chance to Crit. The system will “pull a number out of a hat” so to speak. If that number is between 0-60 you will Crit. If it is between 61-100. You won’t. This can also refer to who the AI chooses to target first on your team. Similar concept but 0-20 targets first character 21-40 targets second etc etc. Or whether debuffs/special effects trigger similar to Crit concept. RNG plays a very large role in the vast majority of turn based games.