WPF Windows Overview
Users interact with Windows Presentation Foundation (WPF) standalone applications through windows. The primary purpose of a window is to host content that visualizes data and enables users to interact with data. Standalone WPF applications provide their own windows by using the Window class. This topic introduces Window before covering the fundamentals of creating and managing windows in standalone applications.
CLik on MSDN link -> http://msdn.microsoft.com/en-us/library/ms748948.aspx
