As in any market, and in particular in crypto, prices can be volatile and are ever changing. For a swap transaction this means that the exchange rate is always fluctuating. As a result, your swap transaction may not result in the amount you thought it would.
When swapping with a fixed rate, our partner Changelly guarantees you a fixed exchange rate. You know exactly in advance how much you are going to receive. For this reason, the fees are higher than a floating rate. When choosing a fixed rate, a user has 15 minutes to send the money.
With a floating rate, you are not protected against variations in crypto prices. The swap rate will depend on the market price at the time of the swap. This option offers lower fees.