A swap rate (also known as rollover) is the interest fee added to or deducted from a trading position when it is held open overnight. Swaps are applied at the end of each trading day, specifically at 23:59 server time.
In forex trading, swap rates are calculated based on the interest rate differential between the two currencies in a pair, as well as whether the position is long or short. This means traders effectively pay interest on the currency they are selling and receive interest on the currency they are buying.