A mortgage and a lien on property are often used interchangeably, but they are not exactly the same thing. A mortgage is a debt instrument secured by the collateral of specified real estate property, while a lien on property is a claim on property that secures the payment of a debt. In other words, a mortgage is the loan itself, while a lien on property is the legal right of the lender to take possession of the property if the borrower defaults on the loan.