Regarding Web Dynpro Abap View Context Binding

Hi,

Iam in the initial stage of learning ABAP web dynpro .Kindly provide the solution for my querries.

1. why do we need to map context of component controller with view context?

2.why do we need to bind the view context with UI element?

3.Diff between view controller and component controller.

Regards,

Aruna