RNG is an invaluable tool for making games more interesting. Unpredictable outcomes may be surprising and will sometimes provide an extra challenge that you'll have to deal with. Other times it may work in your favor, rewarding your efforts in a much more generous way than you'd expect.
RNG stands for Random Number Generator, and it refers to the element of chance or randomness in video games. In gaming, RNG is often used to determine various outcomes, such as the damage dealt in combat, the likelihood of finding rare items, or the success of certain actions.