A lien is a legal encumbrance that was placed on the title and reflects that money is owed against this property. That way, the property cannot be sold or transferred without the money being paid. In other words, you can lose the house to a lien. It's similar to having a mortgage or "securing debt" in that the property is involuntarily pledged against that amount needing to be paid.

These people with the property that has a lien, have a significant issue to resolve.