Forex Swap
Once a foreign exchange transaction settles, the holder is left with a positive (or long) position in one currency, and a negative (or short) position in another. In order to collect or pay any overnight interest due on these foreign balances, at the end of every day institutions will close out any foreign balances and re-institute them for the following day. To do this they typically use tom-next swaps, buying (selling) a foreign amount settling tomorrow, and selling (buying) it back settling the day after.