What this means is that it was acquired through non-payment of taxes or a tax sale. Because of the nature of those sales, it takes longer to get a deed for a new buyer and transfer title so it takes longer to close. Due to the potential of issues with these types of sales, the price is usually much lower than a similar lot sold in a regular market listing. Title insurance is highly recommended if you were to buy it.
If you need someone to assist you with a purchase, I can recommend a good agent in the Pass Christian area.