Silverlight 1.0:
Silverlight 1.0, which was developed under the codename Windows Presentation Foundation/Everywhere (WPF/E), consists of the core presentation framework which is responsible for the user interface (UI), interactivity, and user input, basic UI controls, graphics and animation, media playback, Digital Restrictions Management (DRM), and DOM integration
Silverlight 2:
Silverlight 2 (previously referred to as version 1.1) includes a version of the .NET Framework, implementing the same full Common Language Runtime (CLR) version as .NET Framework 3.0. The XAML markup as well as the code is compiled into .NET assemblies which are then compressed using Zip and stored in a .xap file.
Silverlight 3:
Silverlight version 3 was released in July 9, 2009, which is an extension to Silverlight 2.0, and mainly provides improvements in graphics capabilities, media management, application development areas (additional controls, enhanced binding support, and out-of-browser functionality), and integration in the designers' Expression Blend 3 tools.
Silverlight 4:
Silverlight version 4 was released on April 15, 2010 (along with Silverlight 4 tools for developers).
