Grinding - This is a term used to explain the amount of time needed to build character experience, power, strength, and items. In games like Monster Hunter World, this is a common feature of the game.

Easter Eggs - Usually irrelevant features hidden within a game that you can either find or unlock. Oftentimes they are nods to other games, films, or general gaming culture.

Boss - Usually a very powerful foe in a computer game. These often represent points where you need to "up your game" skills to defeat them to progress.

Glitches - Bugs in the game. These can be hilarious and frustrating in equal measures.

Farming - Gathering items and supplies necessary for progressing in the game. This could be to build some weapons or armor for example.

Camper - A player who doesn't really do anything in a game - especially during shoot-em-ups. This is frowned upon so make sure you're proactive.

Trolling - The act of being overly provocative just to get a reaction.

Mats - Means materials. Usually referring to in-game resources for building stuff like weapons etc.

n00b (Noob) - Refers to a new player or "newbie". Don't be offended if you are on the receiving end of this, but it can be used as an insult. Its usually meant as friendly banter.

Owned - Used to refer to the fact you were badly-beaten in a game.

Grrr - Pretty self-explanatory.

AFK Away From Keyboard. Pretty self-explanatory.

GLHF Good luck Have Fun. Again self-explanatory.

NPC Non-player Character. This is the game controlled character, not controlled by a real player

MOB Monster or Beast. Usually, a boss character or monster that needs to be defeated.

PvP Player vs. Player. Easy enough.

DLC Downloadable Content. Usually paid for extra content, but not always.

RTS Real Time Strategy. It’s a game where everything from strategizing an attack or defend happens in real time or in the moment.

GTG Good to go. Self-explanatory.

DPS Damage per Second. Again self-explanatory.

BRB Be right back. Player needs to pop away from a moment. Toiler break/grab a drink etc.

TLDR Too long, didn’t read. Easy enough.

IGM In-game name. A fake name used to name your online Avatar.

FTW For the win. The other player approves of what you are saying