Mortgages are long term loans that you take out when buying a property. And when we say "long term", we mean it. You might be paying off your mortgage for up to 35 years!!
Notice the word's similarity to depressing things like "mortuary", "mortal" and so on?
Well, we got the word "Mortgage" from Old French "morgage", which literally meant "dead pledge". (Mort = dead, gage = pledge).
So yes, you really should expect to be paying your mortgage off for most of your life! (So make sure you know what you're getting into!)