a MARKET engaged in the buying and selling of FOREIGN CURRENCIES. Such a market is required because each country involved in INTERNATIONAL TRADE and FOREIGN INVESTMENT has its own domestic currency, and this needs to be exchanged for other currencies in order to finance trade and capital transactions. This function is undertaken by a network of private foreign exchange dealers and a country's monetary authorities acting through its central banks.
The foreign exchange market is the "place" where currencies are traded. Currencies are important to most people around the world, whether they realize it or not, because currencies need to be exchanged in order to conduct foreign trade and business. If you are living in the U.S. and want to buy cheese from France, either you or the company that you buy the cheese from has to pay the French for the cheese in euros (EUR). This means that the U.S. importer would have to exchange the equivalent value of U.S. dollars (USD) into euros. The same goes for traveling. A French tourist in Egypt can't pay in euros to see the pyramids because it's not the locally accepted currency. As such, the tourist has to exchange the euros for the local currency, in this case the Egyptian pound, at the current exchange rate.