What is Web Dynpro in SAP ABAP?

Web Dynpro is the SAP Netweaver programming model for user interfaces in SAP ABAP. All Web Dynpro applications follow Model-View-Controller (MVC) Architecture. 

The model is the place where you can access system data. A Web Dynpro application must have at least one view which is responsible for showing data in the web browser. The Controller lives in between model and view and formats model data to be displayed in the view.