In UML modeling, models contain model elements (such as actors, use cases, classes, and packages) and one or more diagrams that show a specific perspective of a system.
A model is both a concept and a modeling element. As a concept, a model is an abstraction of a system from a particular perspective and level of detail. As a modeling element, a model and its corresponding model elements appear in the Model Explorer view. These model elements are graphically represented as diagram elements in a diagram.
A modeling project can contain any number of models. You can open and manage each model in the Model Explorer view, and you can open diagrams from more than one model at the same time.
You can use models to do the following things: