Tax deed sales are public sales held for the purpose of paying the delinquent taxes on real property.
The owner of real property has to pay taxes every year on that property. If the owner fails to do so, a tax certificate is issued. Someone, in essence, pays the taxes for them and then they obtain a certificate in that amount on which interest accrues.
After a certain amount of time, the owner of one of those tax certificates can apply for a tax deed sale. The property would be sold to satisfy the tax certificate and convey ownership of the property to the successful bidder at the tax deed sale.