Pirate

A Pirate in the world of One Piece is anyone man, woman or child, who raises a Jolly Roger, whether they commit an act of Piracy or not. This is not, however, usually is not enough to give anyone a bounty but is enough to be arrested by the Marines. Mountain Bandits are said to be the opposite of Pirates and have not been known to get along with each other too well.

There are two types of Pirates in One Piece, but the terms were only in the original Romance Dawn chapter, and have not yet been mentioned in the current version of One Piece.

Types of Pirates
First mentioned in Romance Dawn V.1 the two main types of pirate are the Peace Maine and Morgania. These terms were once again mentioned in Romance Dawn V.2, however they are not mentioned in One Piece itself. This is largely due to the fact most pirates are a combination of both Peace Maine and Morgania ideals.

Peace Maine
Described in Romance Dawn Version 1, a Peace Maine is a Pirate who goes on adventures, and doesn't really care about personal treasures or going around fighting other Pirates. Luffy, Brook and Shanks are both good examples of a Peace Maine (along with their respective crews). Thats not to say, they will not steal treasure from others if is there and the chance is open, but their primary goal is usually not to own it.

Some pirates start out as Peace Maine but may have a life changing experience (possibly a great loss or generally corruption over time) and become more like a Morgania. The best example of this is Crocodile, who is said to have been very much like Luffy in his youth.

Other examples of Peace Maine have included the Saruyama Alliance and Rolling Pirates.

Morgania
The Morgania fight for treasure and personal gain. They are greedy and love to fight just to cause other people pain and misery. Most of the other Pirates Luffy and his Crew meet are Morgania. Luffy dislikes Morgania and only wants to recruit Peace Maine Pirates. Even in the final storyline, primary most One Piece villians are Morgania pirates, such as Buggy, Don Krieg and Kuro to name but a few.

The 4 Blues
Generally outside the Grand Line, most pirates are considerably much weaker then those inside. Often they are left untouched by the Marines because their attention is drawn towards the Grand Line rather then the East, West, North and South blues.

Thats not to say they don't have their share of villainous pirates, even in the weakest of the blues, the East Blue, powerful men like Don Krieg and Arlong were found. Generally few people in the four Blues have access to Devil Fruits or general knowledge on them. Most Pirates seen before the Straw Hat crew entered the Grand Line used weapons in some form.

The Grand Line
While there are individual pirate crews roaming the Grand Line, the more powerful pirates reside in this sea. These are namely the Shichibukai and the Yonkou.

Generally, the weaker pirates are often weeded out by the Marines or Shichibukai before they can get any further. The unfortunate ones don't even make it to their first island due to a lack of understanding on how the weather works on the Grand Line. The Grand Line is where you're most likely to see Devil Fruit users, both in and out of pirate crews.

In the second half of the Grand Line the most powerful pirates are the Yonkou. The second half of the grand Line (dubbed the "New World") is their playground and it forms a rather dangerously balanced part of the One Piece world.

Prior 1522
Pirates have long been a part of the way of life of the One Piece world. The oldest group of pirates mentioned was the Rumba Pirates, of which Brook was a member of, however their group died 50 years before the storyline began. However, from the various flashbacks so far in the series, there seemed to be a huge absence of pirates despite this.

Then all this changed with the arrival of the great Pirate Gold Roger. Roger set about doing what no one had done before - conquering the Grand Line. He succeeded and in doing so made his way to Raftel and left behind somewhere in the world, his most prised possession One Piece. Roger brought about an air of romance about being a pirate and upon his death his final words sent others to sea to become a pirate. However, things would never be the same again.

The Golden Age of Pirating
The death of Roger sent many pirates to the Grand Line, hoping to find his treasure and become the Pirate King. However with the new wave of pirates came a new change that even Whitebeard noted.

Over the next few decades the old figures of the pre-pirate age began to disappear due to the span of time. This has left fewer and fewer people aware of the days of pirating before Roger's death. Many old values shared by the pirates of the pre-pirate age have slowly began to die. Even once commonly sung songs like Bink's sake have begun to fade out of memory, save from the minds of all but those who still remember the olden days of pirating (such as those like Brook and Shanks). Although newer pirates still adopt these values some completely go in a different direction, the most prominent is Doflamingo who speaks of a new age were pirates stop dreaming.

With the Great Age of pirating spiraling out of control, this has led to the World Government to become deeply concerned. In response they created the Shichibukai and sent them out to kill other pirates. They also allowed themselves to easily be tricked by Spandam into a plan to gain Pluton, unaware that he had alternative motives in mind.