Silverlight is a cross-platform .NET runtime, cross-browser plug-in, and a set of Windows-based developer tools for building RIAs. At its heart, Silverlight is an implementation of the concepts and standards from Windows Presentation Foundation (WPF) such as binding, the property system, and Extensible Application Markup Language (XAML) in a crossplatform version of the .NET Common Language Runtime (CLR) and libraries.