The document discusses the theory of constraints (TOC) and its application to project management. It describes how TOC was developed in the 1950s-1970s and focuses on identifying the constraint or bottleneck in a system and improving its throughput. The document provides an example of using TOC to schedule 3 projects by identifying the resource with the longest task duration as the constraint and prioritizing its tasks to be completed first to maximize throughput. It illustrates the schedule and resource allocation over time to finish all projects as quickly as possible by focusing on the constraint resource.