PK means player killer which actually means a player that kills other players
as it is now if you are killed by a PKer then you loose one stack of items from your inventory unless they are soul bound items like travel gear or equipment you have worn
but if you kill a PK you get all there items and gold but not only that the PKer also looses all there lvls and skills
though im unsure whether they just start over from scratch or they have to make a new account if they are killed hoping a PKer that has died or glitchless is willing to answer this question