an agreement to exchange two currencies is called a(n)
Currency swap [1][2]A cross-currency swap's (XCS's) effective description is a derivative contract, agreed between two counterparties, which specifies the nature of an exchange of payments benchmarked against two interest rate indexes denominated in two different currencies. It also specifies an initial exchange of notional currency in each different currency and the terms of that repayment of notional currency over the life of the swap.
Reserve currency After World War II, the international financial system was governed by a formal agreement, the Bretton Woods System. Under this system the United States dollar was placed deliberately as the anchor of the system, with the US government guaranteeing other central banks that they could sell their US dollar reserves at a fixed rate for gold.[8]