Forex market trading is trading money, currencies worldwide. Most all countries around the world are involved in the forex trading market, where money is bought and sold, based on the value of that currency at the time. As some currencies are not worth much, it is not going to be traded heavily, as the currency is worth more, additional brokers and bankers are going to choose to invest in that market at that time.
Forex trading does take place daily, where almost two trillion dollars are moved every day - that is a huge amount of money. Think about how many millions it does take to bring about a total of a trillion and then consider that this is done on a daily basis - if you want to get involved in where the money is, forex trading is one 'setting' where money is exchanging hands daily.