TOC is the abbreviation of "Theory of Constraints". Prof. Eliyahu M. Goldratt, an Israeli physicist, expressed this theory in a novel called "Goal". Our activities are constrained by a bottleneck. For example, when four people are working together to produce products, three of them can finish each part in a minutes, but it takes 2 minutes to do his part. This product can be output every two minutes. Although three people can do 60 pcs per hour, the other person can make only 30 pcs in an hour.
If you want to know about it, why don't you read "The Goal" or books about "Theory of Constraints"?