A loan payment, consisting of principal and interest, that is the same each month. Because the total payment amount remains fixed, the amount applied against principal each month varies. An example is a mortgage payment.
A mortgage payment that includes principal and interest. It is paid regularly during the term of the mortgage. The payment total remains the same, although the principal portion increases over time and the interest portion decreases.
A mortgage payment that includes both interest and principal repayment. The amount of interest taken from each payment reduces while the amount applied to principal reduction increases over time, but the payment remains constant.