Pirate

A Pirate in the world of One Piece is anyone, who raises a Jolly Roger, whether they commit an act of Piracy or not. This is not, however, usually 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 and it's doubtful they still apply to it.

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, and in Wanted! chapter 5, 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. Even the final version certain amount of pirates display these original concepts, though the actual terms are no longer used.

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 all good examples of pirates based on the old Peace Maines (along with their respective crews) from Romance Dawn. That is not to say that they will not steal treasure from others if it is there and the chance is open, but their primary goal is usually not to own it and greed is generally not their motivation. More often than not, a Peace Maine pirate sees his or her own crew as their most valuable treasure, and to them, not even the legendary treasure of One Piece can match the value of each crewmate.

Some pirates start out as Peace Maine but may have a life changing experience, possibly a great loss or general 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. Gecko Moria, stating that he was exactly like Luffy until he lost his crew in the New World. Peace Maines have been described in Wanted! Chapter 5 as a pirate that goes on adventures funding themselves off the spoils of battles with Morganeer's.

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 them and only wants to recruit Peace Maine pirates. Even in the beginning storyline, most One Piece villains are based on the concept of Morgania pirates, such as Buggy, Don Krieg and Kuro. The Peace Maine pirates however, only steal from them, so it is safe to say that the relations between the two aren't the best.

Morganeer pirates don't see their crew as a valuable asset to them and will easily kill them for 'opposing' them as demonstrated by Don Krieg. Kuro also didn't think twice about slaughtering his own men, and the only sympathy he showed towards his crew was that because Luffy stopped him that they would have to suffer. Luffy was shocked to see Kuro slashing his own men half to death. Also, many of the Morganeer type pirates shown in One Piece don't dream at all, and if they do, it's about achieving world domination or something along the lines of that.

The Four Blues
Generally outside of the Grand Line, most pirates are considerably weaker than 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, or South Blue oceans.

That is not to say that they do not have their share of villainous pirates, as 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 of them. Most pirates seen before the Straw Hat Pirates entered the Grand Line fight by using of some form of weapon, the only exception being Buggy (whose Devil Fruit was found by the Roger Pirates, in the Grand Line).

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.

The Pirate King
Pirate King (called King of the Pirates in the English versions) is the strongest pirate alive and owner of the legendary treasure that was later dubbed as "One Piece". "Kaizoku-Ō" (海賊王), the source of the term, literally means "Pirate King".

The term "Pirate King" was originally a simple nickname for Gol D. Roger to distinguish himself among swashbucklers. Upon Roger's execution, the name was romanticized by the people of the One Piece world into an actual title, much in the same way One Piece itself was simply "Roger's treasure" until the Pirate King's death. In the English manga and anime, "Pirate King" clearly marks this distinguishment ; although Gol D. Roger was Pirate King, Monkey D. Luffy seeks to become the new Pirate King 22 years later.

Before his death, Pirate King Gol D. Roger hid the One Piece. It was rumored to be located at Raftel, the island at the end of the Grand Line. The frenzy over discovering and owning such a massive treasure sparked the "Great Age of Pirates". Until One Piece has been claimed, there will be no current Pirate King.

Until his death, the closest person to becoming the Pirate King was Whitebeard (Edward Newgate). Many people who had met Luffy, such as Coby and Helmeppo, believe that he will be the Pirate King ; Kokoro also addressed Luffy as the Pirate King and Shakuyaku has stated that both she and Silvers Rayleigh were rooting for Luffy to achieve this goal.

The reasons for a person wanting to be the pirate king vary, people like Blackbeard and Gecko Moria wish to have it for the power and influence the title would come with, while others like the Yonkou are considered candidates for it because they're extremely powerful and very close to it, but the two shown so far appear to not have any interest in it. And still others like Luffy and Crocodile (prior to the event that caused him to let go of it) wish to become the pirate king because it is a dream of theirs. Luffy (and Crocodile in his youth) seem to want it for the adventures that are involved with becoming the Pirate King. The Pirate King is said to be the ruler of the sea (Enel asks Luffy about the country the Pirate King rules [after Luffy says that he will be one], Luffy answers this by saying that the Pirate King is the king of the sea, Enel then says that that would be a very interesting title). When talking to Silvers Rayleigh, Luffy said that the Pirate King is the person with the most freedom on the sea.

Before the Golden Age
Pirates have long been a part of the way of life of the One Piece world. The oldest known group of pirates mentioned were the ones under Dorry and Brogy from more than 100 years ago. However, despite pirates existing back, none of them were noteworthy enough to shake the world.

Then all this changed with the arrival of the great Pirate Gol D. 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 something somewhere in the world, his most prized 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. 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 Binks' 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 where pirates should stop dreaming.

With the Great Age of Piracy 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. The World Goverment also allowed themselves to easily be tricked by Spandam into a plan to gain Pluton, unaware that he had alternative motives in mind.

The New Age
At the start of the storyline, the New Age was fast approaching. This New Age of Piracy was brought upon by changes in the world. Various characters who have mentioned it either spoke of a world on the verge of chaos, or a great age where Pirates no longer chase their dreams.

Related to this incoming age in particular was the capture of Whitebeard's 2nd division commander Fire Fist Ace by the Marines. This significant action resulted in the Shichibukai and Marines assembling together in preparation for a war against Whitebeard himself. During the war, Ace was killed and Whitebeard attempted to take down Marineford. Finally Whitebeard, who held the age of Pirates together, died, leaving his vast terroritories up for grabs by other pirates in the New World. It may also be noted that after Blackbeard took Whitebeard's Gura Gura no Mi power, he said that this age will be "his age" shouting aloud for everyone in Marineford and Sabaody Archipelago (viewing via Visual Den Den Mushi) to hear. Now if this is the "new age" that Doflamingo talks about is the one that Blackbeard mentioned is currently unknown.

With the start of the new image, a new wave of pirates went to sea looking for One Piece, having seen Whitebeard confirm its existence. A number of pirates from the previous era escaped Level 6, and it was noted that new new age also means that the Marines themselves now must change with this new age. However the exact direction this new era will take is still as of yet unknown.

It has been hinted in the manga, though, that it is going farther and farther out of the government's hands, with pirates everywhere, all of which appear to be less and less mindful of the government, with entire islands being taken over (note: it's not confirmed that numerous islands are being taken over, except with Brownbeard, but it is very, very possible). The people of Luffy's hometown note in chapter 590 that "for the past few days we've been seeing pirate ships on the coast, we can't even sleep".

Translation and Dub Issues
There are a few notes about a name of a pirate crew to consider:
 * Despite some of the crews names such as the Red-haired pirate crew, most of the members won't have anything in common with their crews name (i.e. they won't be red haired), Red-Haired would be a direct translation as plurals don't exist in the Japanese language. The crews are almost always named after their captain, in this case Red-Haired Shanks and in non-direct translation his crew would be Red-Hair's Pirate Crew.
 * Kaizoku though is the Japanese word for pirate translates literally to sea thief or Sea robber.
 * Kaizoku-dan itself does not literally mean Pirate Crew but rather would translate to Band of Pirates. Ultimately, a pirate crew should be written down as (for example) Red-Hair's band of sea thieves, to an English speaker, this name makes less sense then Red-Haired pirate crew. It is common for English speakers to use pirate crew rather then band of sea thieves as is makes more sense to other English speakers and has a easier "ring" to the name, similarly how Whitebeard is never called Whitemoustache despite what his name is trying to say.

Trivia

 * Privateers and pirates are often grouped together as one and the same. The only real difference was that privateers can be consider hired "pirates", who were contracted to work for their governments against other nations on the seas, and were generally allowed to do anything they wanted so long as they did not attack their own countries ships. Pirates however, work for no one and worked on their own accords. In One Piece, the Shichibukai are based on "Privateers", however the Straw Hats themselves have done actions that would fall into this classification as well; such as helping Arabasta against Crocodile (orginally Nami only agreed to protect Vivi for a price).
 * The "Age of Pirates" established by Gold Roger, is based on the real world's own golden age of piracy.
 * "Pirate king" was a real historical title of powerful Japanese pirates, operated in the Inland Sea.