Use to allow Minitab to add the displayed terms to the model to create a hierarchical model.
In a hierarchical model, all lower-order terms that comprise the higher-order terms also appear in the model. For example, a model that includes the interaction term A*B*C must also include the terms: A, B, C, A*B, A*C, and B*C to be hierarchical. Hierarchy also applies to square terms. For a model that contains C*C to be hierarchical, the model must also include C.
Models must be hierarchical if you want to produce an equation in uncoded (or natural) units. However, weigh that consideration against the fact that models that contain too many terms can be relatively imprecise and can reduce the ability to predict the values of new observations.