A mortgage is the loan that you take out which is secured against your property that enables you to purchase your home.
The mortgage lender has the option of taking possession of the property and selling it on if the mortgage repayments aren’t made to try and recoup any losses it has suffered.
The lender will charge you ‘interest’ in return for lending you the money. Therefore over the term of the mortgage you will need to pay the lender interest, and repay the amount you originally borrowed fully before the mortgage ends.