Organization development (OD) is the interdisciplinary (i.e. psychology, sociology anthropology and recently, applied behavior analysis) study of how to improve the functioning of organizations. There are three levels of organizational analysis. These include the individual, group and organization environment interface. Organizational design is also an important part of OD as are leadership studies.
One of my degrees is in OD. So please feel free to ask any further questions you may have on this topic.