Free foreign exchange refers to foreign exchange that can be bought and sold freely in the international financial market, also known as "spot foreign exchange" and "multilateral settlement foreign exchange". Foreign exchange widely used in international settlement and payment and freely convertible into other countries' currencies. Countries that issue these currencies have relaxed foreign exchange control and control, some even basically abolished foreign exchange control, while others have implemented strict foreign exchange control, which prevents their currencies from being freely convertible into internationally used foreign currencies and stipulates that their currencies cannot be taken out of the country.