PvP stands for player versus player combat. Outside of sanctioned PvP situations such as sieges and arenas, in order to battle another player on the general field, you must 'force attack' them. To force attack, hold the Ctrl key and double-click on your opponent. You can also hold the Ctrl key and use an attack skill. The only exclusions to the force attack rule are flagged or Chaotic players. When attacking one of the aforementioned, holding the Ctrl key is not necessary: you can simply click on the player to start combat.
Some areas, such as villages, are considered Peace Zones. PvP combat cannot be initiated in these areas. Guard NPCs of any village will attack a Chaotic character whenever they come in contact with one.
PvP gameplay is identified through a color-coded system and is mitigated by the Reputation system. The name of any character who attacks another player turns purple (aggressive), and this also applies to anyone who attacks an aggressive player. Players do not receive penalties for attacking and defeating aggressive characters. However, when attacking and killing characters that are neutral (white colored names), the player's Reputation points and PK count increase and the player becomes a Chaotic character.
Chaotic characters cannot use shop services, and have a high chance of dropping items and receiving the death penalty, Shilen's Breath, upon death. However, a chaotic character with a PK count of five or less will not drop items upon death.
Combat Points (CP) add an extra layer of protection when being attacked by another player. CP acts as a buffer that must be depleted before damage will affect the player's hit points. The CP gauge is found both on your Character Status page (Alt+T), as well as your Character Status window.
If a player is damaged by another player, including by another player's pets and servitors, CP is consumed first with no effect on HP. If the CP is not enough to consume all the damage, HP begins to be consumed.
Like HP, CP is also gradually recovered as time passes. The CP total varies by class and level, recovers over time, and acts as a buffer that must be depleted before damage will affect the player's hit points.