World of Warcraft is Blizzard's flagship MMORPG, which has been running since 2004. It quickly became very popular thanks to the huge following of the Warcraft strategy series, and the more streamlined and accessible gameplay than other MMOs on the market at that time. WoW launched in 2004 for the USA, and in early 2005 for Europe. Since then, numerous additions were released in patches and four paid expansions, of which the latest is Mists of Pandaria, which is currently at the end of its lifecycle, with Warlords of Draenor coming in the Fall of 2014.
In WoW players get to explore the lands which they have gotten to know in the Warcraft strategy series. The Horde and the Alliance oppose each other, with both factions having unique races and starting locations. Players can choose from the Undead, Tauren, Orc, Goblin, Troll and Blood Elf for the Horde, and the Human, Night Elf, Dwarf, Draenei, Gnome, and the Worgen for the Alliance. There are also the Pandaren added in the Mists of Pandaria expansion, whi choose their allegiance after their starting questline. 10 classes are available, with the Monks being unique to the Pandaren, and the Death Knight is a Hero Class with an epic starting experience, which begins with level 55.
The game is heavily quest-based, with the later expansions and the 1-60 Azeroth zones being heavily story-centric and having phased, progressing zones and events. The game heavily focuses on the end-game too, with many PvP battlegrounds, 10 and 25 man raids, Pet Battles, 5-man dungeons with varying difficulty levels, daily quests and more. WoW set the standard for most MMOs out there, and still has a subscriber base ranging in the millions.