From The Urban Dead Wiki
MMORPG, or a Massively Multiplayer Online Role-Playing Game, is a game that enables thousands of players to play in a virtual world at the same time over the internet. See Wikipedia. MMORPGs are popular on the Internet because their persistent nature allows for deeper character development and social interaction than that provided by most computer and video games. MMORPGs often have more than one server, but Urban Dead has only one, meaning that the players themselves shape the story.