A MVVM Light developer creates applications using the Model-View-ViewModel (MVVM) architectural pattern. This pattern separates an application into three distinct parts: the model, which represents the data; the view, which represents the user interface; and the ViewModel, which represents the logic behind the application. The developer creates a ViewModel for each page in the application, and bind it to the corresponding view. The ViewModel contains properties and commands that are used by the view to display data and interact with the user. The developer also writes code to handle events that occur in the application, such as when a user clicks a button or changes a setting.