what is RNG?

Random number generator, crit's are influenced by this.

Random Number Gesus

its another way of saying luck. probably cus 3 letters over 4

Something is given a number scale of when it can happen. In LoL it is just crits on a scale of 0-100. If you have a 40% crit chance then the game rolls a number from 0-100. If the number is 41 you don't crit and if it is 40 you do crit.

In something like runescape it is each individual item has a percentage chance to drop from specific enemies. If it has a .005% chance to drop then you must roll from 0-5 out of 1000 numbers. The base stats given to each item is also on a scale of horrid to perfect. If an item has a range of 50-90 damage the computer randomly selects a number from 50-90.

RNG stands for Random Number Generator, and is used to describe any situation where the computer makes a random decision that affects your outcome. Normally it is used when you get screwed by the computer's random decision. Though it can be used either way.

The term is used quite a bit in MMOs with boss fights, since bosses often have random damage amounts, random crits, and random skill orders which can combine to make "unwinnable" situations.

The biggest RNG in league is who you get matchmade with. Did the AFK/feeder end up on your team, or the opposing team? That's RNG. There are also crits, so if you duel someone and someone wins because of lucky crits, that's RNG.