Swap is the exchange of interest from one currency to another, the difference between the interest of one currency and another in a pair is called a swap rate, there are swap rates that are positive and some are negative, positive interest and negative is determined from the type of transaction carried out (Buy or Sell) and also the interest rates of each currency, so that if there is a change in interest rates from a country then it also results in changes in interest this overnight
This swap is imposed if the OP that we have done lasts overnight, so if the OP has not passed the overnight swap period is not enforced, and for when this overnight time each broker has its own provisions. Positive swaps will benefit us traders who do OP because they get swap interest on the contrary for negative swaps, it is disadvantageous because it gives an additional burden in the form of swap interest. The overnight OP is not swapped to it