The term interests is from mid-15c., "legal claim or right; a concern; a benefit, advantage, a being concerned or affected (advantageously)," from Old French interest "damage, loss, harm" (Modern French intérêt), from noun use of Latin interest "it is of importance, it makes a difference," third person singular present of interresse "to concern, make a difference, be of importance," literally "to be between," from inter "between."
Negotiation interests largely relate to basic human needs. Interests are powerful influences in our decision making processes and include those tangible desires which correspond to the specific problem at hand such as increasing sales or productivity. Interests also link to our more basic human emotions which are housed in our psyche. Some examples might include our need for security, empowerment, inclusion, control, or recognition. It is important to understand your counterparts interests when negotiating.
Interesting plot, influencing an outcome, between the endpoints