RealtyTrac reported Thursday that one in every 389 U.S. housing units was the subject of a foreclosure filing in October. The 332,172 filings during the month represented, a 4 percent decrease from the September figures and was nearly identical to the number of filings in October 2009.RealtyTrac, located in Irvine California, compiles a U.S. Foreclosure Market Report each month by tracking documents filed in all three stages of foreclosure:Notice of Default (NOD) and Lis Pendens (LIS). This is the first legal notification from a lender that the borrower on a mortgage loan has defaulted under the terms of their mortgage and the lender intends to foreclose unless the loan is brought current.Auction - Notice of Trustee Sale and Notice of Foreclosure Sale (NTS and NFS); If the borrower does not catch up on their payments the lender will file a notice of sale (the lender intends to sell the property). This notice is published in local paper and contains information pertaining to the date, time and subject property address.Real Estate Owned or REO properties : "REO" stands for "real estate owned" and typically refers to the inventory of real estate that banks and mortgage companies have foreclosed on and subsequently purchased through the foreclosure auction if there was no offer higher than the minimum bid.