MMOs short-hand for Massively Multiplayer Online Game RPG Role Playing Game
CC – Used as shorthand for "Crowd Control" CC refers to a set of spells and abilities that can momentarily stun or paralyze mobs and players. Crowd control is essential when dealing with large groups of mobs, making a class that excels at CC a highly desirable addition to any group.
Class – A "Class" represents a particular set of in-game abilities which determine the way a player interacts with the world, primarily during combat. The most common class types consist of melee (close-range) offense, melee defender, ranged offense, crowd control, healing and general support.
NPC/Mob – A monster (or humanoid character) controlled by in-game AI, and never another actual player. If the Fellowship from The Lord of the Rings are player-controlled characters, Gollum could be considered a Mob or NPC.
AoE – An "Area of Effect" that generally refers to an area where an ability hits multiple targets.
Aggro – (aggressive)This term can mean a couple things. It can apply to a hostile mob that's noticed a player and is actively attempting to attack said player. However, it can also refer to the amount of “hostility” a player has generated on the mob. Most times, in combat, a defensive class will try to gather as much aggro as possible in order to keep mobs from attacking the more vulnerable group members.
Buff – A temporary boost to a character, usually improving health or another core statistic that improves weapon or magical attack damage. Think of it like a magical injection of caffeinated beverage without any of the drawbacks.
Crafting – A game system designed around the creation by players of in-game goods. Generally, crafted items include weapons, armor, potions, enchantments, dyes, food, drink, and the like.
DPS – "Damage per Second". this term refers to how much damage is being dealt to a target. You'll see its use for both player characters and non-player characters, such as mobs.