The Sicilian Mafia, also simply known as the Mafia and frequently referred to as Cosa Nostra by its members, is an Italian Mafia-terrorist-type organized crime syndicate and criminal society originating in the region of Sicily and dating to at least the 19th century. It is a loose association of criminal groups that share a common organizational structure and code of conduct and honor and present themselves to the public under a common brand. The basic group is known as a "family", "clan", or cosca. Each family claims sovereignty over a territory, usually a town or village or a neighborhood of a larger city, in which it operates its rackets. Its members call themselves "men of honor", although the public often refers to them as Mafiosi. The Mafia's core activities are protection racketeering, the arbitration of disputes between criminals, and the organizing and oversight of illegal agreements and transactions.

Source: Wikipedia