M0: The total amount of physical currency (coins and cash) in circulation within the economy. It represents the most liquid form of money but does not include reserves held by banks.
M1: Includes all of M0 plus demand deposits (like checking accounts), traveler's checks, and other checkable deposits. It represents money that is easily accessible for spending.
M2: Includes all of M1 plus savings accounts, time deposits (like certificates of deposit under $100,000), and money market mutual funds. M2 is broader than M1 and includes money that is slightly less liquid.
MB (Monetary Base): Refers to the total amount of currency in circulation (M0) plus the reserves that commercial banks hold at the central bank. MB includes physical currency plus bank reserves, making it a key measure of the central bank's influence on the money supply.