http://en.wikipedia.org/wiki/Money_Market
A money market is a financial market for short-term borrowing and lending, typically up to thirteen months. This contrasts with the capital market for longer-term funds. In the money markets, banks lend to and borrow from each other, short-term financial instruments such as certificates of deposit (CDs) or enter into agreements such as repurchase agreements (repos). It provides short to medium term liquidity in the global financial system. Money market derivatives include forward rate agreements (FRAs) and short-term interest rate futures.
Trading takes place between banks in the "money centers" (New York and London primarily, also Chicago, Frankfurt, Paris, Singapore, Hong Kong, Tokyo, Toronto, Sydney, Mumbai, San Francisco).