A short sale is a real estate sale where the market value of the property is insufficient to pay the mortgage and/or other liens secured by title to a property. 

Why should it concern you if the seller is not going to realize enough money from the sale of a property to pay his or her debt? 

When you enter into a contract to purchase a home the seller is agreeing to deliver clear title to the property. 

Delivering clear title requires the seller to secure a release of any lien (i.e. mortgage lien, judgment lien, tax lien) filed against the property. 

If the property is not worth more than all the liens filed against title to the property (without even considering the real estate commission, attorney fee and other closing costs the seller will incur to complete the sales transaction) the claims against the property are not going to be satisfied in full. 

There will be a need on the seller’s part to attempt to negotiate with the lien holders to release their claims without being paid in full. 

In other words, unless the seller has a pool of money to dip into to pay the liens off to clear title, the agreement to sell a property for the amount you offered in the contract to purchase is going to require the approval or agreement of other parties besides you and the seller.  If you want to get an idea of how many other parties there may be, you might consider checking the public records.  There are risks associated with pursuing a short sale transaction.  You should educate yourself to them and by all means, engage an attorney who has experience in the area of short sale transactions.