A MMORPG (massively multiplayer online role playing game) is a game in which players from all over the world take control of unique (often self-designed) avatars in an online gameworld. Games in this genre frequently take place in fantasy or sci-fi settings much like other Action/Adventure games. MMORPGs, like other role-playing games, are what Simon Egenfeldt Nielsen et al. might call "process-oriented games:" instead of giving the player one, ultimate objective, the game offers a system with which the player can endlessly interact.  For example, in World of Warcraft, a player may complete a quest-line in an area in the game, but might continue to slay monsters for the sake of leveling up or saving up for a new item. In MMORPGs, then, there is no ultimate goal beyond what the player prescribes for him or herself.
MMORPGs share many elements with other kinds of role-playing games, including but not limited to setting, character creation, and quests. Narrative is usually incorporated in to MMORPGs through quests, tasks that the player can complete in order to gain a reward, whether that reward be in-game currency, experience points to improve the character's abilities, or items. In MMORPGs where there is a main storyline for the player to follow, quests might be linked together to form a long narrative; however, these "main quests" are often accompanied by "side quests:" shorter, optional narrative units that are not essential for progression in the game. In this way, the narrative of MMORPGs are non-unilinear, a term videogame scholar Sebastian Domsch uses to describe narratives that the player can shape by choosing the order in which (or whether or not) they complete quests.  Though non-unilinear narratives are not unique to MMORPGs, they allow the player flexibility in choosing how much he or she wants to participate in "processes" offered by the system of the game.
The flexibility the non-unilinear narratives in MMORPGs' gameworlds allows for players to engage in quests individually or in groups; indeed, the way in which MMORPGs allow a large number of players to coexist in a gameworld together via a server is what sets them apart from other kinds of videogame RPGs (see Action RPG and JRPG). Players might band together temporarily in "parties" to defeat certain enemies that might be too strong for an individual to overcome. In other MMORPGs players can also join "guilds" (sometimes known as "clans," "kinships," or "crews") which function to bring players with similar goals in contact with one another.  In this way, MMORPGs offer a variety of social options which can help the player achieve his or her desired experience.
The ancestor of all MMORPGs as we know them today is the pen-and-paper role-playing game, Dungeons & Dragons. Commercially released in 1974, D&D capitalized on the popularity of the fictional world of J.R.R. Tolkien's The Lord of the Rings trilogy. D&D originally allowed players to choose between four races (human, hobbit, dwarf, and elf) as well as between three classes (wizard, warrior, and cleric).  Furthermore, D&D required a "dungeon master" to use the game's rules in order to create adventures for other players to experience. As D&D became popular, similar pen-and-paper role-playing games began to emerge using similar frameworks by which players could both create and verbally enact adventures.
The popularity of D&D and other pen-and-paper role playing games gave rise to computer text adventures based in similar fantasy settings like Colossal Cave Adventure (1976) and Zork (1980).  When these single-player text adventures became similarly popular, others began to create multi-user dungeons (or MUDs), which allowed for several players to access a server and experience text adventures at the same time. For example in the first MUD (referred to as MUD1), players could make changes in the gameworld that other players could register. Players could chat with one another and, in some MUDs, even engage in player versus player combat. 
As technology improved, companies began to produce what were first known as graphical MUDs, and later, the earliest MMORPGs. In 1991, Stormfront Studios released Neverwinter Nights, the first MUD to incorporate graphics.  The game was available through AOL in the years 1991 through 1997. Neverwinter Nights spurred the creation of other graphical MUD in the 1990's, including the popular 1997 release of Ultima Online. Ultima Online operated on a ten-dollar per month subscription fee, making it a predecessor to today's popular subscription-based games. In its first year Ultima Online gained over 100,000 subscribers, demonstrating the growing commercial potential of massive multiplayer online worlds. 
In the 2000's, MMORPGs reached unprecedented levels of popularity and financial success. At the brink of the new mellenium, Sony Online Entertainment released EverQuest which improved upon Ultima Online's crude, isometric graphics, by offering a fully 3D world. It also offered an wide variety of races and classes for players to choose from for character creation.  In 2004 Blizzard Entertainment released an online spin-off of the Warcraft franchise, World of Warcraft, or WoW. Like Ultima Online, and EverQuest before it, WoW also operated (and still operates) on a subscription basis. By 2011, WoW had gained over 12 million subscribers, and is still today one of the most successful videogames in the world. 
Not to be confused with the BioWare game of the same name, Stormfront Studio's 1991 Neverwinter Nights is the first game that resembles a modern MMORPG, though it was considered to be a graphical MUD at the time of its release. As a whole, the game still relies heavily on mechanics from earlier text adventure games. Though the game offers rough graphical depictions of the gameworld in first person, it still relies on textual descriptions appearing on the bottom of the screen to alert the player to details. For instance, players might see an unmarked door on the screen, but the text will inform them that the door leads to a "General Item Store." Alternatively, they might see only an empty pathway but the text will alert them to the presence of a beggar or an old woman with whom they might interact, despite that these NPCs are not represented on screen.
The way in which battle sequences appear in Neverwinter, however, have more in common with today's fantasy MMORPGs. For instance, the perspective changes from first to third person so that the player can view his or her own character, as well as enemies and other players nearby. In this turn-based combat mode, the player can move an icon representing his or her avatar and attack enemies in order to earn experience and treasure.  Though the turn-based system still relies on a text adventure formula to describe the damage done to enemies, it allows for a representation of movement around the battle field. Furthermore, it allows for multiple players in a party to coordinate attacks in order to achieve victory. In this way, Neverwinter Nights might be seen as a bridge between the entirely text-based MUDs before it, and the graphical MMORPGs that would become wildly popular in its wake.
World of Warcraft
As described above, Blizzard's 2004 World of Warcraft is the world's most commercially successful MMORPG. But why is it so popular? Indeed, the game does not include any particularly innovative elements expanding beyond typical fantasy RPG fare. Leveling, experience points, quests, classes, and races do not vary drastically from those presented by games such as EverQuest released in previous years--it seems as though WoW merely represents the best implementation of these common characteristics. However, some would argue that the game is revolutionary in that the developers consciously try to make the game accessible for more casual players than other MMORPGs. 
Indeed, in an article discussing Blizzard's success with WoW, journalist Rob Fahey remarks on the way in which Blizzard uses its user data to cater to a broader casual base instead of its hardcore fans. Fahey points to the way in which WoW's expansions seem to target players that do not spend hundreds of hours grinding for levels, but rather those who appreciate the exploration and quest narratives the gameworld provides. He states: " Mists of Pandaria is the most blatant example yet, though; it's heavily exploration focused, clearly aimed at attracting younger players (there's an assumption in many parts of the media that the panda theme is a pitch at the Chinese market, but it seems far more likely to be aimed at pulling in tweens and young women) and filled with systems that are designed to provide an easier experience and sociable alternatives to end-game raiding, such as the new Pet Battle system."  Though the general public might imagine the typical MMORPG player as a socially inept teenage boy, Blizzard aims WoW at everyone, making a genre that was once for only the most hardcore fans more accessible to newcomers and casual gamers who are still willing to pay the subscription fee. In this way, WoW doesn't just represent a strong example of a genre, it also shows how the genre can evolve.
Star Wars: The Old Republic
Star Wars: The Old Republic (or SWTOR), was released in 2011 and quickly became the fastest growing MMORPG of all time, accruing 1 million subscribers only three days after its launch mid-December.  Unlike other games in the genre discussed above, SWTOR takes place in a setting inspired by science fiction rather than fantasy. Furthermore, the gameworld reflects a fictional world popularized by George Lucas' Star Wars films. In this way, SWTOR is not a standalone game like Neverwinter or a part of a broader gaming franchise like WoW. Indeed, SWTOR might even be said to be a kind of Advergame which advertises other products that are part of the popular Star Wars franchise.
And yet, such a description seems to undermine the power of what SWTOR actually does in its representation of an already-existing fictional universe. By allowing players to customize characters and align themselves with either the (good) Jedi Knights, the (bad) Sith, or the (neutral) smugglers, SWTOR allows its players to enact virtual lives in the context of a fictional world, granting them the opportunity to experience the Star Wars series in a way that they otherwise could not do with the films and various spin-off series alone. Indeed, the idea of the virtual world filled with other human players is what is most appealing about MMORPGs, especially ones that emulate popular fictional worlds: they allow for a fulfillment of fantasy that cannot be attained by games that do not incorporate other players. SWTOR gets at the heart of this kind of wish-fulfillment and desire for a communal experience.
Significance and Criticism
The growing popularity of MMORPG games seems to reflect an increasing interest in process-oriented games that allow for continuous interaction with fictional gameworlds and their non-unilinear narratives. Indeed, in a way MMORPGs are the closest videogames come to a "virtual reality." By creating an avatar that closely represents what form the player wishes to take in the gameworld (whether or not it actually resembles the player), the player attains a sense of individuality within the gameworld. Because the avatar can resemble a player (or the player's fantasy version of him/herself) and because the player's words and actions are associated with that avatar by other players, that avatar can feel rather like a virtual "version" of the player. Furthermore, being able to communicate with other players might make gameplay seem more like real life than it would in other games wherein the player can only interact with repetitive NPCs.
The social elements of MMORPGs (chatting, parties, guilds, and so on) may also allow for these games to have consequences outside the gameworld. Though it presents a satirical view of MMORPGs and the people who play them, Felicia Day's webseries The Guild reflects this possibility. In the series, the protagonist Cyd Sherman (known better by her avatar's name, "Codex") meets and forms real-life relationships with members of her guild. Codex's experiences with her fellow guild members, though humorous, reflect the manner in which MMORPGs can draw people together outside the context of the gameworld. Indeed, as videogames become more prevalent in daily life, games that help form and facilitate relationships between players will become more and more important in the future.
The worlds of MMORPGs do not always represent a utopian virtual world with endless possibilities. Indeed, one of the most common criticisms of MMORPGs is that over time they become boring to the player. Because many of the games within the genre operate by offering new quests and items at certain levels, players must sometimes work or "grind" for experience points in order to make progress toward their goals. Depending on the game, it can take hours and hours to gain a level or complete a quest so that the process feels more like work than fun. Furthermore, quests in themselves can be thankless and repetitive. For example, in what is commonly known as the "gather" or "collection" quest, a player must search for items, sometimes having to kill large numbers of enemies to find the required objects.  While the player will receive a reward for accomplishing his or her goal, in the end that virtual reward may not seem worth the amount of time spent on completing the quest.
In addition, even though MMORPGs can feel immersive insofar as players can easily interact with one another, many elements of the genre can also break the sense that the player is actually in the gameworld. For instance, a player's guild might have to wait to fight a boss battle against the strongest enemy in a dungeon because another guild has just defeated the monster and it needs time to re-spawn in the same place. Even if the players aren't playing to enjoy the quest narrative, knowing that another group is carrying out the exact same quest to receive the exact same reward make the players aware that their actions really do not have that great of an impact on the fictional world they are inhabiting.
- Understanding Video Games, Simon Egenfeldt-Nielsen, Jonas H. Smith, Susana P. Tosca
- Storyplaying, Sebastian Domsch
- How MMORPGs Work
- Neverwinter Nights (MMORPG)
- Blizzard's success isn't magic; just hard work and open minds
- Star Wars: The Old Republic Jumps to Light Speed
- Quest (video gaming)