Several categories of conventional loans exist, the most common and familiar being the fixed rate mortgage. In the cases of fixed rate mortgages, the borrower will lock in an interest rate, and pay down both the principal and interest on the loan at that interest rate every month until the mortgage is paid off. The most typical term of a fixed rate loan is 30 years, though fixed rate mortgages can also be obtained for much shorter terms, the primary difference being in the size of the monthly mortgage payment.