What is the role of the model in the MVVM architecture and why is it necessary?

In MVVM (Model-View-ViewModel) architecture, the Model is responsible for working with the application's data and business logic. It interacts with data sources — databases, network services, repositories — and provides data in a convenient form for the ViewModel.

The Model is necessary for separation of concerns: it isolates the logic of data retrieval and processing from the user interface, which simplifies maintenance, testing, and scaling of the application.