Dungeons & Dragons (as D&D or DnD) is a fantasy role-playing game (RPG) originally designed by Gary Gygax and Dave Arneson, and first published in 1974 by Tactical Studies Rules, Inc. (TSR). It was derived from miniature wargames with a variation of the Chainmail game serving as the initial rule system. D&D's publication is widely regarded as the beginning of modern role-playing games and the role-playing game industry.  D&D departs from traditional wargaming and assigns each player a specific character to play instead of a military formation. These characters embark upon imaginary adventures within a fantasy setting. A Dungeon Master serves as the game's referee and storyteller, while also maintaining the setting in which the adventures occur. The characters form a party that interacts with the setting's inhabitants (and each other). Together they solve dilemmas, engage in battles and gather treasure and knowledge. In the process the characters earn experience points to become increasingly powerful over a series of sessions.

The early success of Dungeons & Dragonsled to a proliferation of similar game systems. Despite this competition, D&D enjoys a nearly unassailable market position in the role-playing game industry. In 1977, the game was split into two versions: the more loose, open framework game system of Dungeons & Dragons and the much tighter and more structured game system of Advanced Dungeons & Dragons(abbreviated as AD&D or ADnD). AD&D 2nd Edition was published in 1989. In 2000, the original version of the game was discontinued and the AD&D version was renamed simply Dungeons & Dragons with the release of its 3rd edition. These rules formed the basis of the d20 System that is available under the Open Game License for use by other publishers. Dungeons & Dragons version 3.5 was released in June 2003, with a 4th edition in June 2008.

As of 2006, Dungeons & Dragons remains the best-known and best-selling role-playing game, with an estimated 20 million people having played the game and more than US $1 billion in book and accessory sales. The game has been supplemented by many pre-fab adventures as well as commercial campaign settings suitable for use by regular gaming groups. Dungeons & Dragons is known beyond the game for other D&D-branded products, references in popular culture and some of the controversies that have surrounded it. The game has won multiple awards and has been translated into many languages beyond the original English.

Dungeons & Dragons is a structured yet open-ended role-playing game. It is normally played indoors with the participants seated around a table-top. Typically, each player controls only a single character, which represents an individual in a fictional setting. As a group, these player characters (PCs) are often described as a ‘party’ of adventurers, with each member often having his or her own areas of specialty. During the course of play, each player directs the actions of his or her character and its interactions with the other characters in the game. A game often continues over a series of meetings to complete a single adventure, and longer into a series of related gaming adventures, called a ‘campaign’.

The results of the party's choices and the overall storyline for the game are determined by the Dungeon Master (DM) according to the rules of the game and the DM's interpretation of those rules. The DM selects and describes the various non-player characters (NPCs) the party encounters, the settings in which these interactions occur, and the outcomes of those encounters based on the players' choices and actions. Encounters often take the form of battles with 'monsters' – a generic term used in D&D to describe potentially hostile beings such as animals or mythical creatures. The game's extensive rules – which cover diverse subjects such as social interactions, magic use, combat, and the effect of the environment on PCs – help the DM to make these decisions. The Dungeon Master may choose to deviate from the published rules or make up new ones as he or she feels necessary.

Massively multiplayer online role-playing game (MMORPG) is a genre of computer role-playing games in which a very large number of players interact with one another within a virtual game world.

As in all RPGs, players assume the role of a fictional character (often in a fantasy world), and take control over many of that character's actions. MMORPGs are distinguished from single-player or small multi-player RPGs by the number of players, and by the game's persistent world, usually hosted by the game's publisher, which continues to exist and evolve while the player is away from the game. This is often reffered to being offline, or AFK (away from keyboard).

MMORPGs are very popular throughout the world. Worldwide revenues for MMORPGs exceeded half a billion dollars in 2005, and Western revenues exceeded US$1 billion in 2006. In 2008, Western consumer spending on subscription MMOGs grew to $1.4 billion. World of Warcraft, a popular mmorpg, had over 11.5 million subscribers as of December, 2008.

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, approximately four 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. The third expansion set, Cataclysm, was announced at BlizzCon 2009.

With more than 11.5 million monthly subscriptions, World of Warcraft is currently the world's most-subscribed MMORPG and holds the Guinness World Record for the most popular MMORPG by subscribers. In April 2008,

World of Warcraft was estimated to hold 62 percent of the massively multiplayer online game (MMOG) subscription market.