What is shichibukai?

The Shichibukai (literally meaning "Seven Warlords of the Sea") are a group of seven powerful pirates who have agreed to work with the World Government and the Marines in exchange for various benefits, such as pardons for past crimes and a degree of freedom to operate as they please. The members can either resign or be dismissed by the Government after certain circumstances. They are one of the three great powers of the world, along with the Marines and the Four Emperors. Each member of the Shichibukai possesses immense power, and they are collectively regarded as some of the strongest individuals in the world of One Piece. The members of the Shichibukai are Crocodile, Dracule Mihawk, Boa Hancock, Jinbe, Bartholomew Kuma, Donquixote Doflamingo, and Edward Weevil(Formerly Blackbeard).