A lien (also called a judgment) against a property means that a previous property owner didn’t pay somebody. In order to collect their monies, the creditor applies a lien against the property. One cannot aquire a deed until all liens are satisfied. By law, government liens supersede private liens (taxes first). The first recognized private lien is a mortgage.
Incredibly, you can sell a property with judgments (liens) against the deed. The buyer then assumes all responsibility for repayment. This is important because there are property owners in our city that casually “sell” properties under land contract. It looks like a rent-to-own situation, but the seller is perpetually tricking the buyer into assuming their debt. Buyer moves out; repeat.