M1, M2, and M3 are progressively more inclusive measures of money: M1 is included in M2, which is included in M3.
M1, the most narrowly defined measure, consists of the most liquid forms of money, namely currency and checkable deposits.
The non-M1 components of M2 are primarily household holdings of savings deposits, small time deposits, and retail money market mutual funds.
The non-M2 components of M3 consist of institutional money funds and certain managed liabilities of depositories, namely large time deposits, repurchase agreements, and Eurodollars.