Trading currency is a type of investment method. Currency trading, as it is more common, is also known as foreign exchange, or FOREX. In this form of exchange, the currency from one country trades against another country's currency. This occurs with the expectation that the value of the currency will rise or fall over the investment period. The process of trading currency occurs on a global scale and is set up much like a stock market. Investors hope to purchase currency at a low price and then will hold it until the value of the currency rises. This trading occurs over the course of the day as well as over the long term.