The traditional fixed rate mortgage is the most common type of loan program, where monthly principal and interest payments never change during the life of the loan. Fixed rate mortgages are available in terms ranging from 10 to 30 years and in most cases can be paid off at any time without penalty. This type of mortgage is structured, or "amortized" so that it will be completely paid off by the end of the loan term. Adding a principal payment on top of your normal payment can shrink the term length.
Even though you have a fixed rate mortgage, your monthly payment may vary based on changes related to taxes and insurance in your escrow account. If either the property tax or the insurance happens to change, the lender (SWBC or one of our servicers) will send you a notice concerning the shortage and give you options to pay an extra lump sum to keep your payment the same OR increase your overall payment. The principal and interest portion of the payment is fixed for the full term of the loan (unless you are paying it down more quickly with additional principal payments).