A mortgage is a debt instrument, secured by the collateral of specified real estate property, that the borrower is obliged to pay back with a predetermined set of payments. Mortgages are used by individuals and businesses to make large real estate purchases without paying the entire purchase price up front. Over many years, the borrower repays the loan, plus interest, until he or she owns the property free and clear. Mortgages are also known as "liens against property" or "claims on property." If the borrower stops paying the mortgage, the lender can foreclose.