MMORPG usually works on the client-server model. Players are represented in the virtual worlds with their avatars - the graphical image of the character they play. They world itself is usually hosted by a game-provider, that charges money for running the servers. These worlds are constantly updated and changed so that the players always have something new to experience and never lose interest in the multiplayer online games they play, because game-providers receive the biggest part of their revenue from the regular payments, done by the subscribers to keep the access active. Most of the MMORPG games are commercial, though there are some free-of-charge projects which are of the significantly lower quality compared to their commercial counterparts.
MMORPG kind of multiplayer online games is now immensely popular. Some projects claim to have over 200.000 subcribers. The top of the most "playing" countries is strongly occupied by South Korea, though the USA and European countries are also heavily infected with the MMORPG virus.
MMORPG games now attract attention from the scholars, particularly those specializing in economics and psychology. Some of the researches study the relationship between the real economies and virtual economies. Some fall into studying the problems of virtual interaction and socialization, by setting up various tests and researches to be completed by the players involved.
Many of those who become friends in the virtual worlds, transcend their friendship into real life. There are many strong online communities, which organize various offline events, parties; people gather to discuss both the in-game issues and ordinary problems of the everyday life. Some consider this to be the abnormal perversion though I think there is nothing really serious and scary about that. To support my point of view, I should say I know several people, who are very succesful in real life, they manage big businesses, drive posh cars, but one must see their eyes, when they talk about their favorite game. This is something which is worth doing for them. They play. And it is very hard for a businessman to play today without being badly tagged for that.
The National Institutes of Health has provided a controversial study in 1993, which has revealed that those who spend over 20 hours a week playing RPG games are under the risk of serious health problems. Though the study is still not accepted by the general medical community, it is obvious that one should try to decrease the time he spends for his favorite MMORPG. Besides, there is another problem associated with the extended time killing with MMORPG - the players may start losing their social links in real life. There are many stories revealing serious problems inside the family, when one of the members paid too much attention to his computer, killing monsters and other players, forgetting about his spouse and kids.
MMORPG games are great. It's a great fun to kill those monsters, exploring amazing virtual worlds and, yes, even killing other people (meaning the charachters they are represented by, of course). However, this should not take more than it should. Everything is great if you know the limit. And you do, right?