A REO (Real Estate Owned) is a property that goes back to the mortgage company after an unsuccessful foreclosure auction. It is a class of property owned by a lender, typically a bank, after an unsuccessful sale at a foreclosure auction.
After repossession and the property becomes classified as REO, the bank will go through the process of trying to sell the property on its own. It will remove some of the liens and other expenses on the home and try to resell it to the public, either through future auctions or direct marketing through a real estate broker.