Persistent world

A persistent world (PW) is a virtual world that continues to exist even after a user exits the world, and user-made changes to its state are, to some extent, permanent. The term is frequently used in the definition of the massively multiplayer online games and can be considered synonymous with that class of games.

Overview
The persistence comes from maintaining and developing the state of the world in the game around the clock. Quite unlike other types of videogames, the plot and events in a persistent world game continue to develop even while some of the players are not playing their characters. That aspect is similar to the real world where events do occur regardless if they are directly or indirectly related to a person, as they continue to happen while a person is asleep, etc. Conversely, a player's character can also influence and change a persistent world. The degree to which a character affects a world varies from game to game. Since the game does not pause or create player-accessible back-up files, a character's actions will have consequences that the player must deal with.