A Contract for Difference is an agreement to exchange the opening and closing price of a contract, multiplied by the underlying volume of that contract.

Unlike many traditional markets, CFDs offer the added flexibility of allowing traders to go short in a commodity they do not already own.

CFDS also offer the advantage of trading on margin, which means traders only have to deposit a small percentage of the underlying values of the positions they wish to trade. This significantly increases the profit (or loss) potential. Where CFDs differ from traditional investments, such as buying equities, is that there is no physical delivery of the underlying instrument. By buying a CFD, you are investing in the expectation that the price of the underlying market is going to rise; you do not actually own any of the underlying assets that the price is quoted on.

Contracts for difference are a very flexible means of trading, especially due to the ability to 'go short' in a market. 

An example of trading with CFDs:

You sell: 10 CFDs @ 86.90 (predicting a bearish market, meaning you expect prices to fall)

You buy: 10 CFDs @ 86.84

Therefore your P/L would be (8690-8684) x 10 = 6 x 10 = $60