 Medium of exchange is one of the three fundamental functions of money in mainstream economics. It is widely accepted token which can be exchanged for goods and services. Because it can be exchanged for any good or service it acts as a intermediary instrument and avoids the limitations of barter, where what one wants has to be exactly matched with what the other has to offer. Most forms of money can act as mediums of exchange including commodity money, representative money and most commonly FIAT money. Representative and FIAT money often exist in digital form as well as physical tokens such as coins and notes.