A lien is a legal claim or charge on property for the payment of some debt, obligation, or duty. It's essentially a security interest that one party has in the property of another as a guarantee for the satisfaction of some debt or duty. The term can also refer to a right to keep possession of something until some condition is fulfilled, such as the payment of a debt. In essence, a lien gives someone with a legitimate claim against an asset legal recourse if that property is sold or disposed of before their debt has been satisfied.