Sometimes it is easier to understand the concepts of the Theory of Constraints with a practical real world example.

I've lived in a few countries in the world and attended a dentist in each of them. Generally, the model is simple. A dentist works in an office with an ante-chamber waiting area. Patients are seen one at a time. The dentist starts and finishes a patient's dental work before seeing the next. In this model the constraint is the dental office and its contents such as the dental chair. To maximize the Throughput in this system the dental office (and chair) must be kept occupied as much as possible. Everything else is subordinated to this decision. The patient scheduling is done to provide one and only one patient in the chair at any given time.

In America, dentists have learned to elevate the dental office as a constraint. By providing several offices (or chairs in a larger office) per dentist, the chair/office constraint is elevated. In this new model, the dentist him/herself is the capacity constrained resource (CCR). The dentist will hire additional assistants. With this model several patients can be seen at once. Each assistant will take a patient and seat them. The assistant will do as much work as she/he is licensed to perform - only involving the dentist for the actual dental treatment. For a typical 30 minute appointment, a patient may only see the dentist for 5 or 10 minutes.

The net effect is that the number of patients processed by a dentist is increased. As the revenue for the system is generated by dental treatment, i.e. the work of the dentist, then by maximizing the number of patients that the dentist can treat in any given day, the overall Throughput of the system is optimized.