A lien is a claim to a piece of property for a specific dollar amount. It is filed in the county system of records and can be one of the causes of a clouded title.
A “voluntary lien” is a lien that someone agreed to at some point in time. For example, if a seller once obtained a home equity loan on their property, they voluntarily agreed to give the lender a claim to a piece of their property to use as collateral. Likewise, any buyer/borrower who obtains a mortgage voluntarily agrees that the mortgage serves as a lien on the property.
If an owner of a piece of property fails to pay their bills (e.g., a tax bill, garbage bill, contractor bill, etc.), the party who is owed money can file a lien on the property. This is an “involuntary lien.” Once it is filed, the lienholders have a right to a piece of that property, up to the amount of the lien. Liens are generally first-come, first-served; the first person to have a lien on the property is paid back first.