Most traditional banks charge a fee for transactions in foreign currencies. This is usually a percentage fee (something like 1.5 – 3% of the the amount of the transaction), plus potentially a fixed fee. This should be clearly outlined in the document that describes the fees on your account.

These fees are added on top of a base exchange rate. There are a few different exchange rates commonly used, of which Revolut's is usually one of the best, but the differences between them are probably not big enough to worry about.

With Revolut, you get a base amount of free currency exchange, I think 1000 EUR per month. Beyond this, there's an additional fee of 0.5 – 1%. You can increase this amount through a subscription, but he aware that once you start your plan, you need to keep it for at least 12 months, even if you pay monthly.