What is a Short Sale?
A short sale means the seller’s lender is accepting a discounted payoff to release an existing mortgage. Just because a property is listed with short sale terms does not mean the lender will accept your offer, even if the seller accepts it.Be aware that the seller need not be in default — to have stopped making mortgage payments — before a lender will consider a short sale. A lender may consider a short sale if the seller is current but the value has fallen. The seller may have over-encumbered, owe more than the home is worth, so a discounted price might bring the price in line with market value, not below it.’
Information taken from About.com