Massively multiplayer online role-playing game (MMORPG) is a genre of computer role-playing games in which a very large number of players interact with one another within a virtual game world.
As in all RPGs, players assume the role of a character (often in a fantasy world) and take control over many of that character's actions. MMORPGs are distinguished from single-player or small multi-player RPGs by the number of players, and by the game's persistent world, usually hosted by the game's publisher, which continues to exist and evolve while the player is away from the game. This is often referred to as being offline.
Although modern MMORPGs sometimes differ dramatically from their antecedents, many of them share some basic characteristics. These include several common themes: some form of progression, social interaction within the game, in-game culture, system architecture, and character customization. Characters can often be customized quite extensively, both in the technical and visual aspects, with new choices often added over time by the developers. Many games also offer some form of modding in order to allow for even greater flexibility of choice.
Character abilities are often very specific due to this. Depending on the particular game, the specialties might be as basic as simply having a greater affinity in one statistic, gaining certain bonuses of in-game resources related in-game race, job, etc.