There are several types of massively multiplayer online games (MMOs) that belong to the adventure genre. One category is puzzle-based adventure games in which players create characters that interact with the game world primarily through isolated puzzles such as matching card games. Another style of adventure MMOs is oriented more toward world building, such as developing and managing a room or house. Possibly the largest category of adventure MMOs, however, includes combat-oriented games in which players either work together or against one another to advance their characters or to amass a high score or some other measure of success. The actual appearance of adventure MMOs can range from two-dimensional (2D) browser-based interfaces to a fully realized three-dimensional (3D) world.
There is some debate about what aspects contribute to adventure MMOs to differentiate them from game genres such as role-playing games (RPGs) or action games. In general, adventure MMOs deal with characters or situations that have little or no options for statistical customization. The gameplay generally also is based more on real-time movements and decisions, such as jumping or moving falling blocks as opposed to menus. Aspects such as long-term resource management or detailed character advancement and statistics usually are not present or are downplayed within the game balance.
There are many adventure MMOs that are puzzle-based. These games generally look like other MMOs but, instead of focusing on combat or building, players are able to engage in a variety of subgames. The types of games vary from one MMO to the next but usually are easy to understand and play, and they sometimes involve challenging other human players. In certain instances, achieving a high score or beating another player can result in some type of in-game reward.
World building is the focus of some adventure MMOs. These games can involve building a room, castle, plot of land or city and then completing adventures to maintain that area or to improve or customize it. There is an MMO world-building genre that is more simulation-oriented, although adventure-style world-building games are distinctly different, because resources are earned through playing the game and not automatically granted over time.
The largest genre of adventure MMOs includes combat-oriented games. These games frequently rely on the reflexes of the players to overcome challenges that may take the form of hostile enemies and terrain that requires clever jumping to pass. Combat adventure games usually have some type of in-game scoring system, such as gold or experience, which is used either to measure the success of a character or to improve the character over time. Unlike the RPG style of game, the improvements to characters in adventure games are usually fairly generic and may not be permanent.