A Central Bank is the overseer and manger of a country’s monetary policy. It is in charge of controlling and regulating the country’s money supply, this it does through the issue of fiat currency and the setting of interest rates.
Central to the Central Bank’s goals is its aim at preventing inflation, fighting unemployment, and stabilizing the currency system. These things are directly affected by a nation’s money supply. For this reason, Central Banks turn to currency manipulation when a country faces economic turmoil.
In the United States, the Federal Reserve Bank acts the country’s central bank.