The Model-View-ViewModel (MVVM) is a software architectural pattern used primarily in designing user interfaces. It separates the development of the graphical user interface (the View) from the business logic and data (the Model). The ViewModel acts as an intermediary, managing the data and commands between the View and the Model, allowing for a more organized and maintainable code structure. In MVVM, the View displays the data and sends user actions to the ViewModel. The ViewModel processes these actions, updates the Model, and notifies the View of any changes. This separation of concerns enhances testability and facilitates easier updates to the user interface without affecting the underlying logic.