The Model interface is a central part of Spring MVC. It is used to represent the data that will be displayed in the view. The model can contain both simple data, like Strings and Numbers, as well as more complex data types, like Objects and Arrays. The Model interface also provides methods for manipulating the data, such as adding, removing, and updating items. In addition, the Model interface can be used to store information about the state of the application, such as whether a user is logged in or not. Ultimately, the Model interface provides a way for the controller to communicate with the view and pass data back and forth between them.