Avalon is the codename for WPF – Windows Presentation Foundation.
Is the graphical subsystem feature of the .NET Framework 3.0 (formerly called WinFX) and is directly related to XAML. It is pre-installed in Windows Vista, the latest version of the Microsoft Windows operating system. WPF is also available for installation on Windows XP SP2 and Windows Server 2003. It provides a consistent programming model for building applications and provides a clear separation between the UI and the business logic. A WPF application can be deployed on the desktop or hosted in a web browser. It also enables rich control, design, and development of the visual aspects of Windows programs. It aims to unify a host of application services: user interface, 2D and 3D drawing