Windows Presentation Format

In short WPF stands for Windows Presentation Foundation and is the user interface code-name of the presentation sub system in Windows programming model and is used to create user interfaces.

WPF is a new technology that can replace both Windows Forms and ASP.NET. Typically Windows Forms is used to build Windows client application and ASP.NET is used to build Web applications.

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 functionality you need to build, run, execute, and manage Windows Vista applications.

How do I build WPF Applications?

To build WPF application, you must install .NET 3.5 SDK. You can also also Visual Studio 2010 and 2008. These two comes with WPF. If you are a student or beginner, you may want to try free version of Visual C# Express 2008 here.

To download the following click here or here
Microsoft Expression Blend is the professional design tool to create connected Windows experiences using WPF.
The Microsoft .NET Framework is a component of the Windows operating system. It provides the foundation for next-generation applications, including WPF and Windows Forms client applications.
Visual Studio 2008 Express Editions are FREE, easy-to-use, and easy-to-learn development tools for developing Windows-based applications. This download includes full language support (compiler, libraries) and the integrated development environment.

Get Started with WPF

Download a free version of Visual Studio 2008, if you do not have Visual Studio 2008 or express version of Visual C# Express 2008 here: Downloads
After that, start learning about WPF in WPF section of C# Corner here:

Learn WPF Programming
Check out WPF FAQ here.
There are some more WPF articles on www.longhorncorner.com
Check out WPF QuickStart Tutorials listing on .NET Heaven
Windows Presentation Foundation, the next generation of Windows UI