Silverlight 2 allows developers to build rich internet applications (RIAs) using .NET and XAML in a web browser. It provides a subset of Windows Presentation Foundation (WPF) functionality and addresses issues with existing RIA technologies like cross-browser compatibility, offline access, and the need to manage multiple technologies. Silverlight 2 brings the .NET runtime into the browser and supports C#, VB.NET, data binding, styles, templates and 30+ built-in controls. It runs in a sandbox isolated from the rest of the system for security.