A theory of change (TOC) maps out and describes the “missing middle” between what a programme or change initiative does (its activities or interventions) and how these lead to the achievement of desired goals. Developing a theory of change requires involves a series of critical-thinking exercises to explore and clarify how and why a desired change is expected to happen, as well as what can inhibits or affect this change process.
Resources
http://www.theoryofchange.org/what-is-theory-of-change/
http://learningforsustainability.net/evaluation/theoryofchange.php