There are many different types of Massively Multiplayer Online (MMO) games in which the focus is on fighting, including both free and pay-to-play titles. Some fighting MMOs focus on the character that players make, allowing them to join in combat directly against computer-controlled enemies and other players. Other games are designed to allow players to use pets or other creatures that do the fighting for them, typically with functionality for catching and training these pets. Fighting MMOs are provided in a number of formats, including games played in a web browser and those that are separate software packages run on a computer.
In general, fighting MMOs are designed for multiple players to populate a single, persistent world and be able to communicate and play together. The major focus, however, is on combat and using the character controlled by the player to fight against enemies in a style similar to single-player fighting games. These opponents are commonly Non-Player Characters (NPCs) that are programmed as part of the game to fight against the players. In some fighting MMOs, there may also be Player vs. Player (PvP) combat in which people in the game are able to fight against each other through their characters.
Other fighting MMOs are designed to allow players to use controlled secondary characters and creatures, such as pets, to be able to do combat against opponents. In these kinds of games, the pets are often fully realized characters or various mythological creatures that can be found and captured to fight alongside the player's character. Training systems are often used in these games by which the pets are able to progress through various "levels" and gain new abilities that can be used in combat. Such fighting MMOs allow players to battle against each other and NPCs indirectly, through the different abilities and attacks gained by their pets.
Different types of fighting MMOs may be available as either free-to-play or subscription-based games, which offer various rates for players. Most free games are only partially free, allowing players to access limited aspects of the game, and letting them pay money to unlock the rest of it. Subscription games, however, usually give the player all of the game, but they must pay a fee each month to continue having access to it. Some fighting MMOs are available as browser-based games; these can be played in a web browser used to access Internet sites. There are also many programs that run as separate applications, usually as software either purchased at a retailer or downloaded from a website.