Specifically, the Camorra were a secret organization in Naples, Italy, engaged in criminal activities, mostly during the 19th century. The equivalent of the Sicilian La Cosa Nostra, but reportedly less formally organized, more distributed and chaotic. The Bourbon rulers of Naples may have also used them as an unofficial secret police that provided thug-for-hire services to quell opposition.
Reputedly, new camorristas were accepted provisionally for a year, and then could not become official members (a Made Man in gangster movie terms) until they had committed a murder for the Camorra.
Most reports suggest that the Camorra came to Naples from Spain, when the Spanish took Naples in the sixteenth century. The Spanish Garduna then became the Camorra.
The camorra still exist, to some extent, as modern organized crime families in Naples. They were very active as heroin smugglers for the Sicilian Mafia in the 1970's and may have sigificant ties to the Russian mob today
The word camorra can be used also to signify any secret group united for unscrupulous purposes.
References:
http://www.encyclopedia.com/printablenew/29729.html
http://www.alleged-mafia-site.com/groups/camorra.htm
http://wordsmith.org/awad/