SWAP: is an exchange of payment obligations generated by some interest rates during a period of time, from the shortest terms (week, fortnight, etc. in the case of Call Money Swap) up to longer terms (20 years).
It typically involves exchanging a fixed interest rate for a variable rate (IRS) or vice versa, to adapt to each company’s balance structure. The interest flows to be charged or paid can be converted into a variable rate (minimising the risk of exposure to movements of these rates) or a fixed rate (stabilising the structure of these flows, eliminating uncertainties).
The charges or payments are calculated as the difference between these exchanged rates and the main sum for calculation is not moved.