Player vs Environment (PvE)

Player Versus Environment, or PvE, is a term used in online games, particularly MMORPGs, CORPGs, MUDs, and other online computer role-playing games, to refer to fighting computer-controlled enemies[1]—in contrast to PvP (player versus player).

Usually a PvE mode can be played either alone, with human companions or with AI companions. The PvE mode may contain a storyline that is narrated as the player progresses through missions. It may also contain missions that may be done in any order. For example, Guild Wars narrates its story by displaying in-game cut scenes and dialogue with non-player characters (NPCs). To enhance replayability, missions can often be completed many times. Characters playing in this mode are often protected against being killed by other players and/or having their possessions stolen. An example of a game where this is not the case is Eve Online, where players can be, and often are, ambushed by other human players player versus player while attempting to complete a PvE mission.

(Source: Wikipedia)