As a Forex trader, it is important to understand what a Forex swap rate is. To keep things simple, the Forex swap rate is the rollover rates you pay or earn to hold your FX positions overnight.
When you trade Forex currency pairs, you are buying one currency and selling the other. When you are long the EURUSD, you are buying the Euro and selling the US dollar.
If you hold the position overnight, you incur an FX swap or swap charges.
We need to consider the current interest rates of both countries you are buying or selling.
You can get a rough idea if it would be a debit or credit by knowing the interest paid on the currency sold and received on the currency bought.