As the name suggests, CFDs are 'contracts' between a buyer and seller. The buyer is the trader, and the seller is the forex broker. The contract says that the buyer will either pay or receive the difference in price in the market between the time they open a position and the time they close it. As you can see, forex CFD trading does not involve purchasing a currency directly.
If the market goes up, the trader receives the difference, but if it goes down, they must pay the difference.
The unit for currency trading is a pip. For most major forex pairs, a pip is $0.0001. The exception is the Japanese yen, which is $0.01 per pip.
Here is an example of CFD forex trading. If you open a CFD position in AUD/USD with your forex broker at $0.7210, the initial value of your position is $0. However, if the market rises to $0.7220, you earn 10 pips, which is the same as $0.0010 per dollar. This amount might not seem significant, but when you engage in forex CFD trading, you use leverage to increase the size of your position.