In most jurisdictions, when a property owner is late on paying real property taxes, the county or municipality will issue a a tax lien on that person's property. Certain states allow the tax lien to become a first lien on the property, which is then turned around and sold at auction as a tax lien certificate.
After placing a successful bid, buyers of a government-issued tax lien certificate will then get one of two things:
1) A state-mandated yield from the lien, which the delinquent taxpayer must pay in order to release the lien, OR