Traders who trade on the Forex basically buy one currency for an amount of money and should that currency appreciate on a given day, the buyer makes a profit. Typically, quantities of currencies are bought in lots, for example 100,000 euros would be the equivalent to 1 lot. The most common traded currencies are Eur/Usd, Gbp/Usd, Usd/Jpy and Usd/Chf.