Mob through RMT
Mob - This term is derived from the term "mobile" in DIKU MUDs. It is generally used now to refer to any NPC that you might choose to kill.
Mount - Mounts are any type of creator or object that a player can ride to increase his or her transportation speed through the game.
MUD - Originally this acronym stood for Multi User Dungeon, and later became Multi User Dimension. It is the general term for online, multiplayer games on the internet. The first MUD, MUD1, was created by Richard Bartle and Roy Trubshaw at Essex University, England around 1978. It is a dramatically superior term than MMORPG, but sadly we are stuck with MMORPG instead of MUD.
Nerf - In the world of gaming, a nerf is a reduction in power, utility, or usefulness of a character class, race, realm, zone, item, etc. Nerfs are very controversial because people do not enjoy being nerfed. Unsurprisingly, people often enjoy seeing OTHER PEOPLE get nerfed… especially in PvP or conflict oriented games.
NPC - Non-Player Character. This is the general term for monsters and other living beings that are controlled by the game itself rather than run by actual users/players. See: mob
Permadeath - Permanent Death. If your character dies in a Permadeath game, you must create a new character. This is an extremely rare feature in the commercial MMO industry.
Persistent Online World - (see: POW)
Pet - A pet is some type of creature, machine, or other object that is in the player's command. It can be an actual summoned pet, something that is trained or captured, a machine that is constructed, or a variety of other similar things. Some pets are actually functional - they fight, gather loot, or perform other tasks. Other types of pets, often called "vanity pets", are simply cosmetic and follow the player around for fun.
PK - See: Playerkilling.
Playerkilling - This is a type of gameplay where players of the game engage in fighting against and killing other players. The increased challenge of going up against another player is what attracts people to this type of gameplay. Some games focus heavily on PK, whereas others forbid it completely.
POW - Persistent Online World. This is a more accurate, but less popular, term for MUDs or MMORPGs. It sounds great, it implies action and excitement, and it is very easy to say. It also focuses on three of the most important elements of an online game: Persistence, the fact that it is Online, and the fact that it is more than just a game, it is a World.
PvE - Player versus Environment. (Sometimes: PvM - Player vs. Monster). This is combat/content that puts the player against the game controlled environment, NPCs, monsters, etc.
PvP - Player versus Player (See: Playerkilling)
Resource - Most MMO crafting systems require that you first gather resources, and then turn those resources into finish products. These resources can be wood, ore, hides, or any manner of base materials (mats).
RMT (Real Money Trade) - This is a category of online commerce that includes the buying and selling of game currency (gold, dil, influence, platinum, etc.), items, characters, powerlevelling services, etc. This is a highly controversial issue in the gaming world. Developers claim to be against it, and so do most players, and yet the market for RMT is over $1 billion USD worldwide.
Roleplaying - Roleplaying or Role Playing is the act of getting into character and acting out a role. People who are roleplaying will generally not engage in any OOC (out of character) communication.
RP - See: Roleplaying
RvR - Realm vs. Realm. A type of PvP content where there are multiple Realms or Kingdoms that wage war against each other. Such wars are generally ongoing as they are part of a constant struggle in the game. Classic examples of this type of gameplay are Dark Age of Camelot and Warhammer Online.
Trade - Trade in MMOs is almost entirely between players. It involves the exchange of goods or services for other goods, services, or coinage. Some games make heavy use of trade between players, whereas in other games it is virtually non-existent.
User Interface (UI) - The user interface is the screen and controls through which you control the game. Many MMOs allow user customized interfaces or at least have moveable interface elements.