The gold standard was a monetary system where currency was backed by and freely convertible to a fixed amount of gold. It was first implemented in Great Britain in 1821 and later adopted by other countries in the late 19th century. The key principles were free movement of gold between countries, automatic expansion/contraction of currency with gold inflows/outflows, and flexible domestic prices. While it promoted trade and stability, the gold standard lacked flexibility and countries eventually abandoned it due to economic and political factors prior to World War 1.