The mechanism for facilitating the purchase and sale of goods，services，commodities， and securities abroad is known as the foreign exchange market．The actual purchase and sale of foreign exchange generally is accomplished through the international departments of large commercial banks．
The demand for foreign exchange can be either transaction or speculative based. The transactions demand for foreign exchange comes from those who wish to make payment to a foreign country for the purchase of a good，a service，or a security purchased from a resident of，or a company located in a foreign country．A resident of the United States wishing to make a remittance to a relative in the United Kingdom would also affect the demand for sterling. The same would be true if the resident of one country wished to make a contribution to a charity located in another country．Speculative demand for a currency is generated by the confidence speculators have in that currency vis-à-vis other world currencies．This demand could be based on political and/ or economic factors，as demonstrated during the 1970s．For example，when the mark was strong and the sterling weak，speculators would sell sterling to buy marks．
The supply of foreign exchange is provided by those who are willing to sell a currency they hold．This may include those who will receive payments in a foreign currency for the export of goods and services，the sale of securities to foreign residents，or the receipt of foreign exchange resulting from gifts or contributions made by foreign countries．International speculators arc also sources of supply when they feel the currency they hold is weak relative to other world currencies．