A non-player character (short NPC) is any person in the game that the player character (PC) can interact with. They are not controlled by anyone but a set AI, but may belong to a certain faction within the game, unlike the PC, who gets a faction just for him/herself. So basically, a NPC is just anyone you meet in the game besides yourself.
A Non-player character or Non Playable Character is any character within a video game that cannot be controlled by the player. This includes most enemies and bosses, although some enemies such as Marach from Final Fantasy Tactics later join the hero's party after circumstances lead them to unite (therefore, Malak is not an NPC though he is an enemy at one point in the game). Allies can also be NPC's however (most damsels in distress fall into this category).
Non-Player Characters, or NPCs, generally refer to non-hostile creatures not controlled by a human player.
Technically speaking, NPCs can actually include both friendly and hostile characters. Though in practice players tend to use the term "Mob" or "Monster" to refer to hostile NPCs/creatures, and not really care about the superset of hostile and non-hostile characters.
Usually, non-hostile NPCs involved in combat (attacking or being attacked) are considered to be allies (even if they don't show up under the "Allies" section of the Party window), although it is not always the case. Most service-providing NPCs (collectors, merchants etc) are not considered allies.
For a complete list of all non-hostile NPC's in the game, see: Category:NPCs
All of the NPCs in the game (friendly, hostile and those that are both) can be found within the species of the Bestiary.
The following are some of the more commonly found NPC types:
See Category:NPCs by type for a more complete list.
A Non-player character, or NPC, is a character not controlled by a player. Players can usually talk to NPCs, but they are not attackable. (If they are attackable, they would be considered a monster) They include store owners, quest contacts, bankers and civilians. NPCs can give out quests, sell items, restrict access to certain areas and perform other vital duties. Many have no useful function, but provide atmosphere or interesting conversation. Some can talk in public, but this will not appear in the chat list. NPCs names have a yellow colour.
NPCs form the foundations for quests: beginning them, continuing the story, giving information and handing out rewards.
RuneScape Classic NPCs could only talk to one player at a time. Players took advantage of this and talked to NPCs and did not respond, thereby holding up the shops (in RuneScape Classic, players who stood in the same spot for five minutes would automatically be logged out, but this rule didn't apply when players were talking to NPCs). Players soon did this with new quests. Jagex changed the system such that if a player doesn't respond to an NPC when others were waiting, then the conversation would automatically end.