This is where you can trade in falling markets, without the need to buy and take ownership of an actual asset. If you think that an asset like a stock or a currency pair is overbought, and you expect the price to drop, you will open a short position, which means you will sell the contract and then buy it back once the price has dropped. Unlike when buying commodities like oil, when trading CFD or forex you can trade even in uncertain or bearish markets. When buying Oil though, if the market turns against you, you may be left with merchandise that is worthless, and without anyone to take the other side of the deal.