In addition to the two standard means of setting the cost of a mortgage loan (fixed at a set interest rate for the term, or variable relative to market interest rates), there are variations in how that cost is paid, and how the loan itself is repaid.
Besides the standard approaches to setting the cost of a mortgage loan (where it's fixed at a set interest rate for the duration, or variable based on market interest rates), there are alternative ways to pay for that cost and repay the loan.