In a negotiation and other areas of business, in addition to knowing your position; what you want, it is important that both sides also know why they want it; interests.
Position: Your pre-determined goals or what you want in the negotiation.
Interests: Your needs, desires, hopes, concerns, fears or why you want what you want. What is motivating you to negotiate?
To negotiate successfully and achieve a win-win outcome you should focus on the interests rather than the position. An open discussion of interests by both sides can help discover the reasons underlying the positions and create a variety of options and possibilities.
Next time you negotiate, dig deep and ask the other side about their interests.