Many people, when selling their home, use the proceeds from the sale to "discharge" or pay off their mortgage loan. If you have a fully "open" mortgage, you can discharge it at any time without penalty. However, if yours is a fully "closed" mortgage, discharging it may require you to pay substantial penalties, often in an amount equal to several months’ interest payments.
There are ways to avoid these penalties, such as taking a "portable" mortgage with you when you sell your present home and applying it to the home you buy. Depending on your specific sales objectives, you may be able to time the sale's completion to coincide with the end of the mortgage term.