A short sale is when the seller/owner of a home wants/needs to sell and they owe more on their mortgage(s) than the home is worth, thereby creating a defecit in funds to pay off the mortgage in whole. The mortgage company has to approve the process because they will be taking a loss. Search through Trulia Q&A and Blog posts about short sales. There is an absolute mountain of information on them. I'm a little surprised by your question. I didn't know there was an agent in American who hasn't heard of a short sale. You need to learn at least a little about them so you can serve your clients. I'll tell you, the most important thing to learn is not to waste your time. They are a pain! Good luck, and please do some research.