The PVP Mode you are playing is dependent on the server you are on. The different types of PVP are:
This is the standard PVP mode. This mode allows you to attack other players in the world. If you kill or die to a player, the dying players loot will drop on the floor. This loot does not include your armor and weapons. You will drop 15% of the materials for your weapon and armor and lose durability on them.
Full Loot PVP:
This is the hardcore PVP mode. This mode allows you to attack other players in the world. If you kill or die to a player, the dying player will drop ALL LOOT on their person.
Raiding a player involves destroying their castle or base and taking loot. This can also include using keys to destroy or capture their castle heart. Castle Heart options are only available on Full Loot PVP servers, although you can raid and loot on normal PVP servers. Typically raiding is restricted to a time schedule.