Mike Gasior does a review of the interest rate swap and talks about its place within the derivatives market. Interest rate swaps are the most popular form of a swap which is performed and Gaisor talks about the risks of each counterparty and discusses the motivate for each party to engage in the swap.
Fixed rate payors will want to convert to floating rate if they believe that rates will go lower; conversely, floating rate payors believe that rates may move higher and therefore will want to convert to a fixed rate. He walks through an example of why a company would want to engage in this.