Forex or FX are just other names for ‘Foreign Exchange’. Forex trading or currency trading is simply the act of buying and selling different currencies, or ‘exchanging’ one currency for another. The Forex market is the largest financial market on the planet, with an average trading volume of roughly $5.1 trillion per day. When you trade currencies with iFOREX UK, you are not buying the actual currencies, but trading on their price, in the form of CFDs.