Examples are cows, woodpecker scalps, cigarettes, etc.
Paper money is the US is fiat , meaning that the value is determined by the government and it works only because people have faith in the system. The most narrowly defined money supply. It consists of only the most liquid of monetary assets, paper, coins, checking deposits in banks, and certain other checkable deposits. The money market funds allow for the writing of checks. Although not as liquid as M1, M2 accounts are still fairly liquid.