Random article: Foreign Exchnage Market Defifnition
Each country emits its own currency. There are plenty of internal and external factors (inflation, deflation, governmental debts, governmental actions, political situation, economic relationship between large players), influencing stability of currency price and leading to its every minute growth or decline.
Forex is a conventional financial market formed in 1970-s of 20th century in the result of switching to floating currency rate. Rapid evolution of technical communication means and computer equipment led to that banks started exchanging currency without mediation of currency exchanges via system of electronic payments.