Your mortgage rates is used to determine your principal and interest payment. Your annual percentage rate is the true cost of the loan once you consider the origination charges and PMI factors associated with your home loan. The higher the origination charges for a mortgage rate and the higher the pmi factor, the higher the APR on a mortgage. Therefore, whenever your see a rate advertised you will also see an APR next to the rate. When comparing different loans its important to compare the APR as well.