An Indepth Look at Akatsuki
Akatsuki in it's kanji written form means daybreak, or red moon as indicated through a breakdown of the word. In the series, there are ten members all of S-Rank level, however since Orochimaru left the group seven years prior, nine have been in count and in circulation since then. They are seen as a threat to all hidden villages and while their members are seen in the bingo book for their home country, since no one truly knows who is apart of the group the rest of the members are not listed.
Within the boundries of a country, Akatsuki are usually split into teams of two people. For example, when Deidara and Akasuna no Sasori first appear in the series they are a team and when the latter died, he was replaced with Tobi. It also seems that with some members, compadiblity is a factor in choosing teams as with Kakuzu and Hiden. Because Kakuzu is known for a terrible temper and killing his partners when it happens, Hiden, who is immortal, is the only one who can travel with him.
Other teams have been shown such as Uchiha Itachi and Hoshigaki Kisame, former teammates, Orochimaru and Sasori, and now, leader Pein and the only kunoichi of the group, Konan; but some members, such as Zetsu have been seen to work alone. Whether this is because of the odd number is unknown, and no reason has ever been given for this. Each group is in charge with various missions and it could range from collecting money, to finding the jinchuuriki (power of human sacrifice).
In a classic style resembling a grim reaper, Akatsuki is known for wearing long black cloaks and rings that are worn on a particular finger. There are ten rings in all, Rei (zero - right thumb), Sei (blue/green - right index), Byaku (white - right middle), Shu (scarlet - right ring), Kai (boar - right little), Sora (sky - left little), Minami (south - left ring), Hoku (north - left middle), San (three - left index), Tama (sphere - left thumb). Each ring is irreplaceable as shown when Orochimaru took his after he left and no member has replaced him. In addition, members have a special technique that seems to be original to them alone such as Itachi's Mangekyou Sharingan for example, as well as Hiden's immortatlity and Pein's Rinnegan.
The goal of this organization was a complete mystery since fans learn of their existance and in chapter 329, the entire plan has been revealed: control the world. Of course it seems like the classic antagonist final goal of many shonen series, but there are three steps that need to be completed before the final goal is in reach. First, the group must obtain money. Second: create the first shinobi mercenary group. Third: collect and harness all the bijuu's powers and seal them in a specific order.
Since the last war ten years prior, the hidden villages were being reduced in size and power. The Five Great Shinbi villages were fine as they had the power and resources, but smaller villages could not and began to downfall. The idea is to not be alligned with anyone and create a force that the villages could hire for cheap. With the power of the bijuu in their hands, they can then create new wars and gain a monopoly over the entire market. In the end, Akatsuki will become more powerful than all the Great Villages, and collapse is imminent forcing them to rely on the S-Ranked criminals.
However, recent chapters have hinted that the bijuu's may have a purpose beyond global conquest, a possibility being that harnessing the creature's powers may very well return his Sharingan to full power.