The document discusses black markets, which refer to illegal economic activity involving goods or services traded in violation of government regulations. Black market transactions typically occur secretly or underground. Reasons for the formation of black markets include government price controls, taxation of goods and services, and obtaining prohibited items. The document provides examples of black market currency exchange rates in Egypt, Argentina, Iran, and Venezuela where government controls have led to high inflation and demand for foreign currencies like the US Dollar on the black market. Other black markets mentioned include rising prices, currency exchange, exotic animals and products, and human organs.