The last time the property was delinquent it was placed on the tax sale list, which entitles people to pay the back taxes and then attempt to collect from the property owner. If the owner does not repay the person who bought the debt within (I think) 2 years, then the owner of the debt can begin foreclosure procedings.
The property owner paid enough to forestall the tax sale so they bought themselves a reprieve. The interest continues to accrue at the rate of 18% (for most of the debt) and there was a year end penalty equal to 3% of the delinquent tax amount added to the balance due.
Do you have a specific question? I have some experts on speed dial :-)