Web Dynpro Window 

A window is used to combine several Views and View Sets. A view can only be displayed by the browser if it has been embedded in a window. A window always contains one or more views, which are connected by navigation links. One of these views, or a view set, is specified as the start view and is displayed the first time the window is called.

Plugs and Window Controller

Windows have, like views,  inbound and outbound plugs. A window controller is assigned to each Web Dynpro window. The window controller is a global controller. It is visible by all other controllers within the component.

Interface View

Each window has a uniquely assigned interface view. This interface view represents the outward view of the window. The interface view is linked with a Web Dynpro application so that the window can be called using a URL.

Furthermore, the interface view enables windows to be reused by multiple components. So in addition to all component-specific views, the interface views of windows of all components that are known by the current component (that is, for which a component use has been created) can be embedded in a window. Just like the view, the interface view has inbound plugs and outbound plugs and can be integrated in navigation structure of another window using these plugs. These are plugs of the appropriate window that are explicitly marked as interface plugs and can therefore be provided to the interface of the component.

Each view can be displayed only once in the current window at the same time; this also applies to an interface view of a used component. It is possible, however, to declare several uses for one and the same component. In this way, you can display an interface view multiple times.