There are two types of characters in the game: Player Characters (PC) and Non-Player Characters (NPCs). A Player Character is a player’s avatar in the world of Azeroth. The color of a PC’s name tag can vary from white, green, yellow or red depending on faction and Player vs. Player (PvP) status. Non-Player Characters are AI-controlled characters that can only interact with PCs through scripted events or artificial intelligence (AI).

There are three types of NPCs. Friendly NPCs, whose names are displayed in green, cannot attack friendly characters and vice versa. Hostile NPCs, whose names are in red, are either of the opposing faction or are mobs (enemies controlled by AI) and will freely attack any PC with whom they are hostile. Neutral NPCs, whose names are displayed in yellow, are neutral and will only attack if provoked.

Some NPC interaction is affected by the reputation a PC has with them. For example, certain NPC merchants will have more items available for sale if that PC has a higher reputation with the merchant’s faction. PCs’ standing with a faction can be increased or decreased by killing certain mobs or handing in items to certain NPCs. However, PCs cannot gain reputation with opposing factions, so a Horde character cannot gain reputation with any Alliance-only faction and vice versa.

NPCs in major and minor cities can buy and sell merchandise, train class and profession skills, give quests and provide a large number of services that are needed in the game. While some will merely offer advice or further the story, others, such as city guards, patrol around set paths to keep cities defended against attacking PCs or hostile NPCs that may attempt to invade.

Characters in World of Warcraft are tied to specific user accounts. User accounts can be used on all servers, or realms. Characters can be moved between servers in the same region (e.g., from one European server to another, but not from a European server to an American one) for a fee. As of this time, one may move a character from a Player Versus Player (PvP) realm to another PvP realm, or a Player Versus Environment(PvE) realm, but one may not move a character from a PvE realm to a PvP realm. The two playable factions currently in the game are the Alliance and Horde both consisting of five different races each. There are a total of 9 playable classes. The Burning Crusade expansion added one new race to each faction (the Blood Elves and the Draenei).