WPF And XAML

Windows Presentation Foundation (WPF) is the code-name of the presentation (user-interfaces) sub system in Windows Vista programming model and is used to create user interfaces. This blog talks about WPF.
What is WPF?
WPF is the engine that is responsible for creating, displaying, and manipulating user-interfaces, documents, images, movies, and media in Windows Vista.
Physically, WPF is a set of libraries that have all functionalty you need to build, run, execute, and manage Windows Vista applications.
What is XAML?
XAML is a new descriptive programming language developed by Microsoft to write user interfaces for next generation managed applications.
How XAML is related to WPF?
XAML is a new descriptive programming language developed by Microsoft to write user interfaces for next generation managed applications. XAML is used in WPF to represent the controls and code with the help of C#, Visual Basic, and other .NET Framework languages.

XAML can be think as ASP.NET and/or Windows Forms in Windows Vista. For example, to write a Web application in .NET 1.0, 1.1, or 2.0, you use ASP.NET and to write Windows Applications, you use Windows Forms. Now in Windows Vista and .NET 3.0, you will use XAML instead of Windows Forms and ASP.NET.

Does that mean XAML will replace ASP.NET and Windows Forms? YES and NO. Both ASP.NET and Windows Forms will also be supported on .NET 3.0 but you don't have to use them if you don't want.
What Operating Systems does WPF support?
Windows Vista, Windows XP, and Windows 2003 Server.
How do I build WPF Applicaitons?
To build WPF application, you must install .NET 3.0 SDK. It can be found on MSDN downloads sites.
What do I need to run WPF Applications?
To run WPF applications, you must install .NET 3.0 SDK redistributable. It can be found on MSDN downloads sites.