Contracts for difference offer all the benefits of trading shares without having to physically own them. Contracts for difference (aka CFDs) mirror the performance of a share or an index. A CFD is in essence an agreement between the buyer and seller to exchange the difference in the current value of a share, currency, commodity or index and its value at the end of the contract. If the difference is positive, the seller pays the buyer. If it is negative, the buyer is the one who loses money.