Interdependence theory attempts to describe the social exchange components of personal relationships. It states that human relationships are basically a cost versus reward scenario with individuals trying to minimize costs and increase the benefits within the relationship.
There are four types of rewards and costs discussed in interdependence theory: emotional, instrumental, opportunity, and social.
Emotional costs/rewards are the positive or negative feelings that occur because of a relationship.
Instrumental costs are the extra work someone has to do because of a relationship (like picking up dirty laundry) and instrumental rewards are the work that is lessened by the relationship (a partner helping with household chores).
Opportunity costs are when someone has to give up something in a relationship (give up a dream job to relocate) while opportunity rewards are when something is gained because of the relationship (relocating to nicer city to live in a dream house).
Social costs and rewards are determined by the social status and proficiency of the partner.
All of these costs and rewards can determine whether or not a relationship is successful. If the benefits of the relationship outweigh the costs then the relationship typically will continue. If the costs are higher than the benefits and other alternatives are available then the relationship will most likely dissolve.