MMORPG stands for "Massively Multiplayer Online Role-Playing Game". MMORPGs are online computer games in which the players create characters that interact in a specifically defined "environment" and with other character-players. Probably the best-known
and suckiest MMORPG is World of Warcraft.
What is interesting from a RationalWiki perspective is that there are many places on the innertubez that are not specifically "game" sites where people play similar games. These include social networking sites such as Myspace, Facebook, etc., as well as other, non-social sites.
The fine art of "sockpuppetry", or creating a "user" persona that is utterly fictional, and then interacting on blogs or wikis, is probably more interesting than playing some silly high-rez version of Dungeons and Dragons. This is because the "character" has to seem "real" and interact with other (presumably) real people. As such, it is an art form made possible by "web 2.0".