NPC is an abbreviation which stands for Non-Player Character, and refers to those characters that do not have a player to control their actions or represent them in role-play. NPCs can be anyone from John and Joan Public bystanders, to supporting characters like maids, police contacts and relatives, or fully powered heroes and villains.
In the case of non-powered mortals, NPCs are fair game while running emitted scenes or general pick-up role-play. After all, what point is there of going to the coffee shop if there's no one to ring up your order? These sorts of every-day individuals have no restrictions on them and can be 'spoofed' to the needs of the scene at hand. They are also free to be used as bystanders and even victims in combat scenes. We simply ask that scenes involving a great deal of destruction or mass casualties get logged and placed on the wiki, otherwise it will not count towards the game's canon.
Read through Temporary Characters for information concerning emitting documented Alternate Identities heroes and villains.