Windows Presentation Foundation (WPF)

The Windows Presentation Foundation (WPF) is the new graphical subsystem in Windows Vista that replaces the old GDI graphical subsystem and makes many of the cool UI features possible. In addition, WPF provides the foundation for a new print subsystem that includes, among other things, support for better color management to allow high-fidelity color printing as well as support for printing advanced effects such as gradients and transparencies. And the key ingredient that ties WPF and print subsystem together is XPS.

WPF was initially released as part of .NET Framework 3.0. WPF is built on DirectX, which provides hardware acceleration and enables modern UI features like transparency, gradients and transforms. WPF also offers a new markup language, known as XAML which is an alternative means for defining UI elements and relationships with other UI elements.
WPF is included with Windows 7, Windows Vista and Windows Server 2008, and is also available for Windows XP Service Pack 2 or later, and Windows Server 2003.

Microsoft Silverlight is a web-based subset of WPF that enables Flash-like web and mobile applications with the same programming model as .NET applications. 3D features are not supported, but XPS and vector-based drawing are included.