In order to serve you better: Charging your credit card in your home currency
Dynamic currency conversion is a service provided by merchants when processing credit cards payable in a foreign currency. Say, for example, you present a credit card issued by a United States bank to a hotel in Ireland, where the Euro is the local currency. In order to serve you better, the hotel will convert the fee from Euros into dollars.
What they don’t tell you is they will use a horrible exchange rate for the conversion.