The black market (sometimes known as underground or black economy) is trade, goods and services that are not part of the official economy of a country; this may be legal activities where taxes are not paid, or illegal activities, such as drug dealing and prostitution.
In modern societies, the underground economy covers a vast array of activities. It is generally smaller in countries where economic freedom is greater, and it becomes progressively larger in those areas where corruption, regulation, or legal monopolies restrict economic activity in various goods, services, or trading groups. (Source: Wikipedia)
