Money originated from the difficulties of bartering and was developed to serve as a medium of exchange. It has key characteristics like being generally acceptable, divisible, recognizable, and having a stated value. Early forms of money included commodity money like precious metals. Modern forms include coins, paper money, and negotiable instruments. Money supply is measured by M1, M2, and M3, which include various types of currency, checking and savings deposits, money market funds, and time deposits.