The Theory of Constraints is a philosophy that is used to identify the point in a process where constraints and bottlenecks prevent the process or system from achieving its highest level of performance. To simplify the definition, the theory of constraints tells us that "the throughput of a system is determined by the systems biggest constraint (bottleneck).
The Philosophy was developed by Dr. Eliyahu M. Goldratt. He covered the philosophy in many different books such as: The Goal and Theory of Constraints. You can click on any of the links in this definition if you are interested in reading one of Dr. Goldratts books.
Dr. Goldratt taught that there were five essential steps used in the theory of constraints. Those five steps are: