"Short sales" or selling a property "short" simply means that a homeowner has fallen behind in payments and is facing the possibility of foreclosure - The bank or lender agrees to accept an offer/sale price lower than what is actually owed by the seller on their mortgage, which results in a successful "short-sale" of a property. There is plenty of specialized knowledge, forms, and proceedures necessary that an agent needs to know in order to successfully complete a short sale. In addition, there are plenty of tax and legal issues that may require you also hire a knowledgable attorney and financial/tax expert well versed in the short sale process.
To give you an idea of how many people are facing, will be or have faced the possibility of their homes being foreclosed on, an article on Housingwire.com dated 9/5/08 detailed amazing numbers for mortgages nationwide - According to this article, "More than nine-percent of U.S. Mortgages were delinquent or in foeclosure at the end of the second-quarter, as both major catagories of borrower default activity hit new records." The numbers are really astounding and as more mortgages continue to reset, the increase in homeowners unable to pay will also increase.
Helping homeowners through this trying time and specialized process to avoid their home from being foreclosured on, is often-times rewarding.