Silverlight combines multiple technologies into a single development platform that enables you to select the right tools and the right programming language for your needs. Silverlight offers the following features:

• WPF and XAML. Silverlight includes a subset of the Windows Presentation Foundation (WPF) technology, which greatly extends the elements in the browser for creating UI. Silverlight lets you create immersive graphics, animation, media, and other rich client features, extending browser-based UI beyond what is available with HTML alone. Extensible Application Markup Language (XAML) provides a declarative markup syntax for creating elements. For more information, see Layout, Input, and Printing¹, Graphics, Animation, and Media², and Controls³.
• Extensions to JavaScript. Silverlight provides extensions to the universal browser scripting language that provide control over the browser UI, including the ability to work with WPF elements. For more information, see JavaScript API for Silverlight⁴.
• Cross-browser, cross-platform support. Silverlight runs the same on all popular browsers (and on popular platforms). You can design and develop your application without having to worry about which browser or platform your users have. For more information, see Supported Operating Systems and Browsers⁵.
• Integration with existing applications. Silverlight integrates seamlessly with your existing JavaScript and ASP.NET AJAX code to complement functionality you have already created. For more information, see Integrating Silverlight with a Web Page⁶.
• Access to the .NET Framework programming model. You can create Silverlight applications using dynamic languages such as IronPython as well as languages such as C# and Visual Basic. For more information, see Managed API for Silverlight⁷
• Tools Support. You can use development tools, such as Visual Studio and Expression Blend, to quickly create Silverlight applications. For more information, see Silverlight Designer for Visual Studio 2010⁸ and Expression Blend⁹.
• Networking support. Silverlight includes support for HTTP over TCP. You can connect to WCF, SOAP, or ASP.NET AJAX services and receive XML, JSON, or RSS data. For more information, see Networking and Communication¹⁰. In addition, you can build multicast clients with Silverlight. For more information, see Working with Multicast¹¹.
• LINQ. Silverlight includes language-integrated query (LINQ), which enables you to program data access using intuitive native syntax and strongly typed objects in .NET Framework languages. For more information, see XML Data¹².

For more details on Silverlight features, see Silverlight Architecture¹³