This is a mortgage for which the rate of interest is fixed for the term, ie, a set period of time. The monthly principal and interest payments remain the same throughout the life of the loan. The most common mortgage terms are 30 and 15 years. With a 30-year fixed rate mortgage your monthly payments are lower than they would be on a 15 year fixed rate, but the 15 year loan allows you to repay your loan twice as fast and save more than half the total interest costs.
Fixed-rate loans generally have repayment terms of 15, 20, or 30 years. Both the interest rate and the monthly payments (for principal and interest) stay the same during the life of the loan.