When purchasing a mortgage, you will usually find mortgages lumped into two main piles: fixed rate mortgages and adjustable rate mortgages (ARMs).
Fixed rate mortgages have been available for decades and usually span a 30 year time period. A fixed rate mortgage is exactly what it sounds like—a mortgage with an interest rate which is fixed and doesn’t alter for the entire time span of the loan, regardless of whatever changes are occurring in the housing market.
Adjustable rate mortgages by contrast change in relation to fluctuations in housing indexes.
These are your standard fully amortized loans. Your principle and interest payment will not change over the course of the loan, as your interest rate is guaranteed not to move for the life of the loan.