According to Beckhard, "OD is an effort planned, organization-wide, and managed from the top to increase organization effectiveness and health through planned interventions in the organization's "processes," using behavioral science knowledge." (Cummings & Worley, 2008). In other words, it is a systemwide application and transfer of behavioral science knowledge to the planned development, improvement, and reinforcement of the strategies, structures, and processes that lead to organization effectiveness. Organizational Development theories can be differentiated into two main categories: Change process theory i.e. How does change take place? and Implementation Theory i.e. How can change strategies be put into practice?.
Change process theory helps the managers to learn how organizations improve and change. According to Lewin, there are three distinct and vital stages of change. The first one is 'unfreezing', a reduction in the strength of old values, attitudes or behaviors. The second one is 'moving', a process of change in thoughts, feeling, behavior or all three, that is in some way more liberating or more productive. And the last one is 'refreezing', the stabilization of change at a new stage of equilibrium. Without refreezing it is easy to backslide into the old ways. Implementation theory concerned with how specific intervention strategies are designed and carried out. "An intervention is a set of sequenced and planned actions or events intended to help the organization increase its effectiveness." (Cummings & Worley, 2008). Interventions are aimed at helping the group become better able to use its own resources to identify and solve interpersonal problems and devise more effective ways of working. There are four types of interventions namely Human Process Interventions, Technostructural Interventions, Human Resources Management Interventions and Strategic Interventions.