World of Warcraft, often referred to as WoW, is a massively multiplayer online role-playing game (MMORPG) by Blizzard Entertainment. It is the fourth released game set in the fantasy Warcraft universe, which was first introduced by Warcraft: Orcs & Humans in 1994. World of Warcraft takes place within the Warcraft world of Azeroth, two years after the events at the conclusion of Blizzard`s previous Warcraft release, Warcraft III: The Frozen Throne. Blizzard Entertainment announced World of Warcraft on September 2, 2001. The game was released on November 23, 2004, on the 10th anniversary of the Warcraft franchise. The first expansion set of the game, The Burning Crusade, was released on January 16, 2007. The second expansion set, Wrath of the Lich King, was released on November 13, 2008. With more than 11.5 million monthly subscribers, World of Warcraft is currently the world`s most-subscribed MMORPG and holds the Guinness World Record for the most popular MMORPG. In April 2008, World of Warcraft was estimated to hold 62 percent of the massively multiplayer online game (MMOG) market.

As with other MMORPGs, players control a character avatar within a game world in third person view (with the option of playing in first person), exploring the landscape, fighting various monsters, completing quests, and interacting with NPCs or other players. In common with many other MMORPGs, World of Warcraft requires the player to pay for a subscription, either by buying game cards for a pre-selected amount of playing time, or by using a credit or debit card to pay on a regular basis. To enter the game, the player must select a realm (or server). Each realm acts as an individual copy of the game world, and falls into one of four rule-set categories. Realms are either Player versus player (PvP), where open combat among players is more common, or Player versus environment (PvE), where the gameplay is more focused on defeating monsters and completing quests; roleplay (RP) variants of both realm types are also available. On a PvP or RP-PvP server a player may create characters belonging to either the Horde or the Alliance factions, but not both. Realms are also categorized by language, with in-game support in the language available. Players can move established characters between realms for a fee. Then the player may either select one of their previously made characters or create a new one.

To create a new character, in keeping with the storyline in the previous games in the Warcraft series, players must choose between the opposing factions of Alliance or Horde. Characters from the opposing factions can perform rudimentary communication and trade, but only members of the same faction can speak, email, group, and share guilds. The player selects the new character`s race (species), such as Orcs or Trolls for the Horde or Humans or Dwarves for the Alliance. Players must also select the class for the character, with choices such as mages, warriors and priests available. Some classes are limited to particular races.

As characters become more developed, they gain various talents and skills, requiring the player to further define the abilities of that character. Professions such as tailoring, blacksmithing, mining, cooking and first-aid can also be learned by characters. Characters may also form or join guilds, allowing characters in the same guild unified communications, a shared guild name, and possibly identity, guild bank and dues. Much of World of Warcraft play involves "questing". These quests, also called "tasks" or "missions", are usually available from non-player characters (NPCs). Quests usually reward the player with experience points, items, and/or in-game money. It is also through quests that much of the game`s story is told, both through the quest text and through scripted NPC actions. Quests are linked by a common theme, with the next quest triggered by the completion of the previous, forming a quest chain. Quests commonly involve killing a number of creatures, gathering a certain number of resources, finding a difficult to locate object, speaking to various NPCs, visiting specific locations, interacting with objects in the world, or delivering an item from one place to another.

World of Warcraft was almost universally praised by critics upon release, following a period of high anticipation before launch. Although the game follows a similar model to others in the genre and was noted for having many familiar concepts from roleplaying games, the new approaches to reduce pauses between game encounters was well liked. A common example was the new approach to character death; in previous MMORPGs a player would suffer a high penalty for character death, while in WoW a player would be able to recover and start playing quickly. Combat was another area where "downtime" or pauses between play were reduced. By allowing all character types to recover from damage taken, players could return to combat quickly. It was felt that these changes in pacing would make the genre more accessible to casual players, who would be able to play for short periods and still achieve something, while still having a depth of game that would attract players at all levels of interest in the genre. The concept of a "rested bonus", or increasing the rate at which a player`s character gains experience was also welcomed as a way for players to quickly catch up with their friends