Money is anything widely accepted as a medium of exchange and provides liquidity. The alternative to money is barter, which is inefficient. There are different types of money including commodity, convertible paper currency, commodity-backed money, and fiat money. The Federal Reserve was created in 1913 and functions as the central bank by setting monetary policy and controlling the money supply through tools like required reserve ratios, interest rates, and open market transactions. The money multiplier estimates how money is created through the reserve requirement ratio of banks. Money supply growth affects interest rates and prices in the economy.