Introduction About MVVM(MODEL VIEW VIEWMODEL)

1) What is MVVM(Model View ViewModel)?
MVVM is a designing pattern of software development which consist three layer Model, View, ViewModel.

1) Model-Model take care about business logic means its data in and transfer to Data access layer.
2) View-View take care about presentation layer means by this user interact with Application.
3) View Model-View model is a abstraction of view layer and its used to bind data.

When Use MVVM                                                                                                                            

MVVM is used when came binding via a data context concept. we can use this pattern in Java Script ,WPF etc