A mob, mobile or monster is a computer-controlled non-player character (NPC) in a computer game such as an MMORPG or MUD. Depending on context, every and any such characters in a game may be considered to be a "mob", or usage of the term may be limited to hostile NPCs and/or NPCs vulnerable to attack. Common usage refers to either a single character or a multitude of characters in a group as a mob. In most modern graphical games, "mob" may be used to specifically refer to generic monstrous NPCs that the player is expected to hunt and kill, excluding NPCs that engage in dialog or sell items or who cannot be attacked. "Named mobs" are distinguished by having a proper name rather than being referred to by a general type ("a goblin," "a citizen," etc.). "Dumb mobs" are those capable of no complex behaviors beyond attacking or moving around.