In RuneScape what is pking

pking is short for player killing which simply means a real player killing another real player i think it has to be without one of the players permission not in al kharad dueling arena or clan wars so the only place you can player kill is on pvp world player verses player world it used to be go onto any world and go to the wildersness and there was pking players killing other players cause you used to be able to anytime in the wildi.