Exchange rate, also known as "foreign exchange market or exchange rate", is the ratio of one country's currency to another country's currency and the price of another currency expressed in one currency. Because of the different names and values of currencies in the world, one country's currency should set an exchange rate for other countries' currencies, that is, the exchange rate. In the short term, a country's exchange rate is determined by the demand and supply of foreign currency. Foreigners buying their own goods, investing in their own countries and speculating on their own currencies will all affect the demand for their own currencies. Domestic residents want to buy foreign products, invest in foreign countries and speculate in foreign exchange, which affects their money supply. In the long run, the main factors affecting the exchange rate are: relative price level, tariffs and quotas, preference for domestic goods relative to foreign goods and productivity.