An NPC (Non-Player Character) is any character you encounter and interact with in World of Warcraft that is not controlled by other human players — they are generated and controlled by the game server. NPCs are either neutral or affiliated with a particular faction (Alliance or Horde).[1] You cannot attack NPCs of your faction and you must be "at war" (set in Reputation tab of your character sheet) with a neutral NPC's faction to attack them.[1]
Neutral or Friendly NPCs may have a bag (, if a vendor) or talk bubble (, if you can talk to them) cursor when you mouse-over them. Some vendors require you to talk to them first.
Pointers for buying or selling:
in range to buy/sellout of range
Pointers for talking:
in range to talkout of range
Other types of NPCs (flight masters, innkeepers, quest givers, trainers, etc.) may have different pointer icons when you mouse over them.