How is the currency conversion rate set?

Anyone know who sets the currency conversion ratio? Also, what standard do they use to set it? Precious metals, an economic theory, a list of factors?|||people buying and selling the currency. People buy the currency the rate goes up, people selling - it goes down!|||The foreign exchange rate indicates the value of any given currency relative to another. The exchange rates can change drastically from day to day depending upon the state of a country鈥檚 economy and various other factors.|||depending upon the economy of a country,each country values its own currency.and based on this valuation the convertion ratio is set.A stronger economy means higher exports and rich cash inflow.