Models are instances of designs. Models are created by Child Rules. You have already placed a number of Models subordinate to MyTable on the Model Tree
Designs can be thought of as the definition of a class of objects. Child rules take a Design, supply it with specific parameters, and create specific instances of that class. These instances are "Models" in kBridge.
Rules don"t have to apply to Designs only. A Model Rule is a Rule that you can rewrite while in an instance. Compare that to a Design Rule, which changes a Design forever (though their Parameters can be overridden to make special instances).
The Children underneath a Child group actually have model Rules. Model Rules are generated at run time by the user, most often to build or fill out the tree.