A foreign exchange (FX or Forex) contract is an agreement between you and a broker to exchange an amount of money equal to the difference between the opening and closing price of an FX position. A contract can be more efficient than just trading directly in the currency, because it means if you were trading in a currency such as US Dollars, you will not need to take possession of a large amount of US currency at the end of the contract (or provide the US currency if you’re trading short) you will simply receive (or pay) the difference in price.
Unlike most stocks, foreign exchange is traded over-the-counter (OTC) meaning that it is traded amongst a network of dealers and brokers rather than directly through a formal exchange like the New York Stock Exchange. In order to engage in trading foreign exchange, you need to buy or sell an FX contract. Traditional retail FX trades are generally for spot and forward settlement of a currency, while institutional investors might make use of more sophisticated trades such as options and swaps.
At Questrade, currency trading is done in pairs - this means you trade in the difference in value between currencies such as the US dollar vs the Euro, or the Canadian dollar against the Swiss Franc. You can trade in lot sizes of 1, 0.1, and 0.01 contracts, which corresponds to 100,000 units, 10,000 units, and 1,000 units of the respective currencies in the contract.