A gangster is a criminal who is a member of a crime organization,prostitution and thats not good. They aslo do drugs which is even worse. The terms are most commonly used in reference to members of the criminal organizations associated with American prohibition and the American offshoot of the Italian Mafia, such as the Chicago Outfit, the Philadelphia Mafia, and the Five Families, and individuals such as Al Capone and Bugsy Siegel. Gangsters have been romanticized in popular culture in films such as The Godfather series, GoodFellas and TV shows like The Sopranos.
As American society and culture developed, new immigrants were migrating to the United States. One of the first influential and popular gangs was the Five Points Gang.  During the late 1800s and early 1900s, the streets of New York were ruled by Irish gangs (Whyos and Dead Rabbits) and Jewish gangs like the Monk Eastman gang.
The stereotypical image and myth of the American gangster is most closely associated with the organized crime entities of the Prohibition era of the 1920s and 1930s. In 1920, the Eighteenth Amendment of the United States Constitution banned the sale, manufacture, and transportation of alcohol for consumption. Many gangs sold alcohol illegally for tremendous profit, and used acute violence to stake turf and protect their interest. Often, police officers and politicians were paid off or extorted to ensure continued operation. Al Capone was one of the most influential gangsters during this period. Born in Williamsburg, Brooklyn in 1899 to immigrant parents, Capone was recruited by the Five Points Gang in the early 1920s. Capone’s childhood friend, Lucky Luciano, was also originally a member of the Five Points Gang. Capone would rise to control a major portion of illicit activity such as gambling, prostitution, and bootlegging in Chicago, Illinois during the early twentieth century.
A Sicilian gangster, Luciano is considered the father of modern organized crime and the mastermind of the massive postwar expansion of the international heroin trade. He is the first official boss of the modern Genovese crime family, and is credited with organizing the American Mafia's ruling body.
Carlo Gambino was an influential gangster in America. He was born in Palermo, Sicily but moved to America at 21. Through his Castellano relatives, he joined the Masseria Family. While Lucky Luciano was the underboss in the Masseria Family, Gambino worked him. After Luciano had Masseria killed, he became the boss and Gambino was sent to the Scalise Family. Later Scalise was stripped of his rank, and Vicenzu Mangano became boss until, 1951 when Mangano disappeared. Albert Anastasia took over the family but in 1957, Gambino had him killed because he wanted to be boss. From 1961 until he died in 1976 Carlo Gambino was the chairman of the American Mafia. Frank Costello was another influential gangster. He was born in Italy but moved to America when he was 4 and changed his name from Francesco Castiglia to Frank Costello when he joined a gang at age 13. He worked with Charlie Luciano in bootlegging and gambling. He also had a lot of political power which enabled him to continue his business. He became in charge when Luciano was arrested and he expanded this operation and became a very powerful man. He decided to step away from the gangster life and died peacefully in 1973.
A Gangster or mobster is a criminal who is a member of a crime organization, such as a gang. The terms are widely used in reference to members of gangs associated with American prohibition and the American offshoot of the Mafia, such as the Chicago Outfit or the Five Families. The related word "mobster" is a term derived from Latin and Aramaic. A gang is a group of three or more people who, through the organization, formation, and establishment of an assemblage, share a common identity.
In early usage, the word gang referred to a group of workmen. In the United Kingdom the word is still often used in this sense.