A currency's Converter value expressed in terms of another is called its exchange rate. Foreign exchange, or FX, is a worldwide, decentralized, over-the-counter market. The market is being traded for currencies. Being and being are the largest. They're marketing to the world. In the market, the credit is being followed. It turns out that one unit of one currency rarely equals exactly one unit of another, which makes the market necessary. The currency As it happens, the purpose of the receipt is to make it easier to pay for equal-value currency units.