M1 money supply includes coins and currency in circulation—the coins and bills that circulate in an economy that are not held by the U.S. Treasury, at the Federal Reserve Bank, or in bank vaults. Closely related to currency are checkable deposits, also known as demand deposits. These are the amounts held in checking accounts. They are called demand deposits or checkable deposits because the banking institution must give the deposit holder his money “on demand” when a check is written or a debit card is used. These items together—currency, and checking accounts in banks—make up the definition of money known as M1, which is measured daily by the Federal Reserve System. Traveler’s checks are also included in M1, but have decreased in use over the recent past.

M2 money supply includes everything in M1 but also adds other types of deposits. For example, M2 includes savings deposits in banks, which are bank accounts on which you cannot write a check directly, but from which you can easily withdraw the money at an automatic teller machine or bank. Many banks and other financial institutions also offer a chance to invest in money market funds, where the deposits of many individual investors are pooled together and invested in a safe way, such as short-term government bonds. Another ingredient of M2 is the relatively small (that is, less than about $100,000) certificates of deposit (CDs) or time deposits, which are accounts that the depositor has committed to leaving in the bank for a certain period of time, ranging from a few months to a few years, in exchange for a higher interest rate. In short, all these types of M2 are money that you can withdraw and spend, but which require a greater effort to do so than the items in M1.