What is Central Bank?

Legal Definition
A central bank, reserve bank, or monetary authority is an institution that manages a state's currency, money supply, and interest rates. Central banks also usually oversee the commercial banking system of their respective countries. In contrast to a commercial bank, a central bank possesses a monopoly on increasing the monetary base in the state, and usually also prints the national currency, which usually serves as the state's legal tender.

The primary function of a central bank is to control the nation's money supply (monetary policy), through active duties such as managing interest rates, setting the reserve requirement, and acting as a lender of last resort to the banking sector during times of bank insolvency or financial crisis. Central banks usually also have supervisory powers, intended to prevent bank runs and to reduce the risk that commercial banks and other financial institutions engage in reckless or fraudulent behavior. Central banks in most developed nations are institutionally designed to be independent from political interference. Still, limited control by the executive and legislative bodies usually exists.
-- Wikipedia
Legal Definition
Empowered by the national government to manage and execute key monetary functions: (1) issue, manage, and preserve the value of the country's currency; (2) regulate the money supply; (3) supervise and provide governance over the operations of commercial banks; (4) serve as a banker's bank and the local lender of last resort. Some Central banks, such as the Bank Of England provide all these functions. Others, such as in Germany and the US, employ two or more organizations. Most Central banks are owned by their respective governments, such as the Bank Of England, Banque De France, Reserve Bank Of India. Still others, such as Belgian Central Bank and Bank Of Japan, have mixed ownerships. Germany's Bundesbank and the US Federal Reserve System are owned by private banks. Bank Of Sweden (1656) was the first Central bank, followed by the Bank Of England (1694) and the Bank Of France (1800). Bank Of Japan was established in 1888, and the US Federal Reserve System in 1913. These central banks are typically autonomous or semiautonomous organizations.