Foreign exchange refers to the means of payment expressed in foreign currency, which can be used for international settlement. It has the following characteristics:

(1) Foreign exchange is a financial asset denominated in foreign currency. For example, the dollar is foreign exchange in countries outside the United States, but not in the United States;

(2) The repayment of foreign exchange must have reliable material guarantee, which can be generally recognized and accepted by all countries;

(3) Foreign exchange must be fully convertible.