Forex is the largest and most liquid market in the world with an average daily turnover of $3.98 trillion. The Forex market is open 24 hours a day, 5 days a week with the most important world trading centers being located in US, UK, Tokyo, Zurich, Frankfurt, Hong Kong, Singapore, Paris, and Sydney. Trading is said to be conducted over the counter it's not like stocks where there is a central marketplace with all orders processed like the NYSE.