A mod or modification is the alteration of content from a video game in order to make it operate in a manner different from its original version. Mods can be created for any genre of game but are especially popular in first-person shooters, role-playing games and real-time strategy games. Mods are made by the general public or a developer and can be entirely new games in themselves, but mods are not stand-alone software and require the user to have the original release in order to run.