The document discusses the Model-View-ViewModel (MVVM) pattern for app design in iOS. It provides an overview of MVVM, describing the model, view and viewmodel components. It outlines some advantages and disadvantages of MVVM. It also discusses using CocoaPods to add third-party libraries to a project and different ways to implement MVVM, including key-value observing, delegation, reactive programming and property binding. The document includes examples of moving business logic from a view controller to a viewmodel and using binding in a project to synchronize views and viewmodels.