The document introduces the Model-View-Controller (MVC) architecture. It explains that MVC is a standard design pattern that separates an application into three main components: the model, the view, and the controller. The model manages the data logic and rules of the app. The view displays the user interface. The controller handles input and converts it to commands for the model and view. MVC makes apps easier to manage, supports test-driven development, and allows for more secure and collaborative development.