Lately, Black Desert added a Duel System. Comparing with PK, players should get formally comfirmation from each other to start the duel. The biggest different point is that there is no other penalty of lose or win.
No matter 1 vs.1 , party vs. party or even 1 vs. party probably happen in Duel System. It is possible for individual or party to apply for combat. If the adversaries promised, all of his party member will enter combat status.
If you want to combat, you need to get close to your enemy and click with mouse to select "Duel" option. Once you receive the duel invite, you will get a message via the popup window. You could browse the oppoent's info and then select to start combat. The both side of duel should be above level 50. The combat does not require other cost and item. Because player who request for duel is under restrciton, players could not fight in safe zone like town.