All forex CFDs involve a currency pair. For example, AUD/USD involves the Australian dollar and the US dollar, while EUR/USD is the symbol of the Euro and US dollar.
What does the symbol mean? The first abbreviation is the base currency, which is the currency you buy. The second is the quote currency, which is the one you sell.
For example, if you see AUD/USD 0.7200, it means you can purchase $1 Australian with $0.72 US.
One of the advantages of CFDs is that it is possible to go long or short on a currency pair. If you go long, you buy the base currency. However, if you go short, you will buy the quote currency (and profit if the base currency goes down in value).