The term "red-light district" is used to refer to an area of a city in which there is a concentration of sex-related businesses such as brothels and shops selling pornography. It can refer to areas in which such activities are legal or it can refer to areas in which such activities (or some of them) are illegal but are carried out nonetheless.
Some cities, such as Amsterdam, have legalized prostitution with red-light districts that are completely legal. Other cities simply have informal red-light districts where prostitution is common even though it is not legal.
The term "red light district" is used to describe an area populated with brothels and other sex-related businesses and activities.
The term originated as a result of the red lights used to illuminate the front of a brothel, making it easily identifiable.
Some red light districts operate legally, in areas where prostitution and other solicitation is legal. Other areas operate against local regulations and are monitored and enforced by local authorities.