This is what the urban dictionary says:
Gangster
There are two types of "gangster":
1) A wannabe thug, often illiterate and an inhabitant of a downtrodden ghetto that hangs around in "gangs"; largely associated with the African-American subculture. These try-hard wanna be "gangstas" attempt to make themselves appear like real criminals by graffiting buildings, smoking/selling drugs and trying to looking all "bad-ass and macho an'-shit, yo". An utter degradation of what true gangsters represent (see below), and street wannabe "gangsta"-types don't hold a candle to what real gangsters are.
2) The *real* gangsters are those behind organised crime; most notably the Mafia. Responsible for blackmarket trade, epsionage, organised beatings/assassinations, etc. "The Godfather" portrays the archtype of true gangsters, showing the brutality of mob beatings, shootings, running rackets and abusing woman, alcohol and everything in between. The real gansters are *not* to be confused with the aforementioned definition, commonly used as it might be.
