A lien is a legal claim or right against a property that allows a lender or creditor to take possession of the property if the borrower fails to meet their obligations, such as repaying a loan. This claim ensures that the lender has a way to recover their money, often through the sale of the property. There are different types of liens, including mortgage liens, which are tied to real estate, and mechanic's liens, which can be placed by contractors for unpaid work. Liens can affect the property owner's ability to sell or refinance the property until the debt is settled.