Money Supply, or Money Stock, refers to the total amount of money available in an economy to the general public at a given time.
There are several ways to look at money supply:
M0: The amount of physical currency in circulation in an economy.
M1: M0 + checkable deposits (such as checking accounts).
M2: M1 + small time deposits (such as savings accounts).
M3: M2 + large time deposits (such as large-denomination time deposits).
L: M3 + liquid and near-liquid assets (such as Treasury bills).