Interests are the underlying desires and concerns that motivate people to take a position. While their position is what they say they want, such as "I want to build my house here!", their interests are the reasons why they take that position (because I want a quiet lot with a good view of the city). Often parties' interests are compatible, and hence negotiable, even when their positions seem to be in complete opposition.

Interests are what matter to a person; their views; concerns; desires; what motivates them; or why they ask for or insist on things.  (see Positions)

Interests include an individual's or group's hopes, expectations, fears, concerns, beliefs, values and needs. Interests must be considered and reflected in an agreement to satisfy the parties involved and reach sustainable outcomes.

Interests are what compel people to negotiate. Interests lie behind positions. Interests may include a party's desire for economic security, military security, political recognition/legitimacy, sovereignty, political autonomy or representation, sustenance, or specific underlying goals that motivate the person or party to seek concessions or acceptable solutions to a dispute, problem, or business opportunity.