|Turf Mechanics|The Turf System is a system that allows players to conquer territories across the sea by taking islands under their protection. The benefits of conquering territories are two-fold. Firstly, they give you a bonus income per completed thread while the territory is under your control. And secondly, they provide you with a base of operations that can be built upon further for various perks. It also provides grounds for staging important character-developing RPs and is a good way to influence the world around it too. Keep in mind that you "owning" an island does not necessarily mean you are its ruler. It simply means that the island is under your protection while it is ruled autonomously by whoever you designated as its official ruler.
NPC is short for Non-Player Character and is a character created to be in a single or a few select locations throughout the six seas. There are rewards for defeating almost every single NPC, but it of course varies from level to level. They are called non-player character (NPC) is any character in a game which is not controlled by a player, but rather it will work as a community project. People will need to help out, as this is not a task that can be handled by a handful of people if there are tens of players looking to fight them. So once someone enters a new island, one or more person will be assigned the role of roleplaying the characters on said island, to fight against them. You are expected to be helpful in this regard.
Players who are roleplaying as these characters will also receive the same degree of experience as if it were their own characters. It gives players the opportunity to try out a devil fruit or fighting style they are not familiar with, and this can get players excited about hosting.
There are two types of NPCs. There are those that have names give to them, and those that are simply a base name such as "Marines" or "Straw Hat Pirates" with a number next to them. These number signifies how many of them there are. The named ones are often higher level than the unnamed ones, which usually referred to as fodder. While named characters will only be controlled by the person(s) in charge of that island, invading players are allowed to state things that the fodders do within the combat, and finish them off quickly, as long as it is within reason(plot and power-wise).
Pirate Crews can of course take over islands that are other crew's territory, but since the NPCs will by then be defeated, they will instead spend 14 real-life days before capturing the territory. This is to encourage battles between pirate crews. As long as the crew has purchased a spy on the said island or left an NPC, they will be alerted and can make their way to stop the takeover. This of course is only if they are within traveling distance from the island. Should the defenders arrive too late, they are instead the ones that will have to wait 14 real-life days and fight off the other crew.