The largest financial market in the world is open around the clock. It has no central exchange. It is also the most competitively priced. Yet only a minority of private investors trade it, despite the fact that in the UK it can be accessed tax free by opening a financial spread betting account. This market is the foreign exchange market, also known as forex or FX.Most people only trade currencies when they change money on holiday. But currency trading also represents a great alternative market to shares. This is because currencies are traded in pairs’: by using a currency spread bet or CFD (contract for difference), you are backing one currency against the other. Nobody talks about the forex market being up or down, because whenever one currency is losing’, another is winning.You will usually see a currency trade quoted by your s fiat currency pread betting company as a pair of three-letter codes. Every currency traded in the market has a three letter code. For example, sterling is usually quoted as GBP, while the US dollar appears as USD. If you saw GBP/USD on your spread betting screen, the price next to it would be the number of US dollars that could be bought with one pound. If you then bought’ GBP/USD, you would be expecting to profit from a rise in the pound. If you sold’ it, you would be backing the dollar to strengthen against the pound (the number would go down as less dollars would be needed to buy a pound).Spread betting and CFD trading also lets you profit from changes in currency prices by using margin: your spread betting company or CFD broker is lending you the bulk of the value of your trade by only requiring you to deposit a portion of it, your margin.