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Making money through CFD
What is being described in Longson's answer, though helpful, is perhaps more similar to a financial spread bet. Exactly like a bookmaker, the provider of a spread bet takes the other side of the bet, and is counter party to your "trade". A CFD is also a bet between two parties. Now, if the CFD provider uses a market maker model, then this is exactly the same as with a spread bet and the provider is the counter party. However, if the provider uses a direct market access model then the counter party to your contract is another CFD trader, and the provider is just acting as an intermediary to bring you together (basically doing the job of both a brokerage and an exchange). A CFD entered into through a direct market access provider is in many ways similar to a Futures contract. Critically though, the contract is traded 'over-the-counter' and not on any centralized and regulated exchange. This is the reason that CFDs are not permitted in the US - the providers are not authorized as exchanges. Whichever model your CFD provider uses, it is best to think of the contract as a 'bet' on the future price movements of the underlying stock or commodity, in much the same way as with any other derivative instrument such as futures, forwards, swaps, or options. Finally, note that because you don't actually own the underlying stock (just as Longson has highlighted) you won't be entitled to any of the additional benefits that can come with ownership of a stock, such as dividend payments or the right to attend shareholder meetings. RESPONSE TO QUESTION So if I understand correctly, the money gained through a direct market access model comes from other investors in the same CFD who happened to have invested in the "wrong" direction the asset was presumed to take. What happens then, if no one is betting in the opposite direction of my investment. Your understanding is correct. If literally nobody is betting in the opposite direction to you, then you will not be able to trade. This is true for any derivative market; if suddenly every single buyer were to remove their bids from the S&P futures, then no seller would be able to sell. This is a very extreme scenario, as the S&P futures market is incredibly liquid (loads of buyers and sellers at all times).  However, if something like this does happen (the flash crash of 2010, for example), then the centralized futures exchanges such as the CME have safeguards in place - the market become locked-limit so that it can only fall so far, there may be no buyers below the lock limit price, but the market cannot fall through it. CFD providers are not obliged to provide such safeguards, which is why regulators in the US don't permit them to operate. It may be the case that if you're trying to buy a CFD for a thinly traded and ill-liquid stock there will be no seller available. One possibility is that the provider will offer a 'hybrid' model, and in the absence of an independent counter party they will take the opposite side of your bet, and then offset their risk by taking an opposing position in the underlying stock.