Fed Funds

From Reuters Financial Glossary

Reserve balances deposited at the Federal Reserve Bank by US commercial banks. These funds can be lent out to other member banks to meet short-term reserve requirements and the rate at which they are lent is known as the Fed Funds rate. This is one of two key US interest rates, the other being the discount rate. Fed Funds can also refer to the money used by the Federal Reserve to pay for its purchases of government securities

See also: Discount Rate, Federal Reserve System