At the end of a Sprint the product development team will demonstrate the functionality they have created. A Scrum Team delivers potentially shippable code.
This is Rule # 1 of Scrum. All other principles of Scrum are equally important but this is the most equal one :). During the Scrum Trainer Retreat this year I found out that Mitch Lacey has a passion about this topic. He wrote an extremely interesting chapter for his book which you can read on his website. He calls this chapter simply: “Defining Done” I strongly recommend that you read this part of the book. Mitch talks about this important activity which you have to do before starting the sprint — to get a clear understanding what you have to deliver.