Warcraft is a franchise of video games, novels and other media originally created by Blizzard Entertainment. The series is made up of four core games: Warcraft: Orcs & Humans, Warcraft II: Tides of Darkness, Warcraft III: Reign of Chaos, and World of Warcraft. The first three of these core games are in the real-time strategy genre, where opposing players command virtual armies in battle against each other or a computer-controlled enemy. The last and best selling title of the franchise is a massively multiplayer online role-playing game (MMORPG). Expansion sets were also released for multiple games in the series, each adding more content to each game as an effort to expand the product life span of each. Warcraft: Orcs & Humans had no expansions, Warcraft II had Warcraft II: Beyond the Dark Portal, and Warcraft III had Warcraft III: The Frozen Throne. World of Warcraft has had multiple expansions, namely World of Warcraft: The Burning Crusade, World of Warcraft: Wrath of the Lich King and World of Warcraft: Cataclysm.