Because the world consists of more than two countries, the exchange rate between two countries, called the bilateral rate, tells little about the exchange rate versus other currencies. Almost all financial papers report both ways. Since foreign exchange is just another commodity, the direct way is intuitively easier to understand. It is the number of home currency units necessary to buy a unit of the commodity. Fifty dollars per pair of shoes is more usual than 0.02 shoes per dollar.
Market forces insure that the various exchange rates are brought into alignment.
If there are any discrepancies between exchange rates of currencies in different markets, called the cross rates of traded currencies, arbitrage will eliminate the difference. The speed of today's communications ensures that currencies cannot stay out of line for long. Arbitragers keep a watchful eye on the possibility of cross-rate inequality. This is a sure source of profit with no risk by buying and selling instantaneously in two different locations. There are several markets for foreign exchange.