This document introduces Roslyn, an open source .NET compiler platform that provides code analysis APIs. It allows building code analysis tools like those used in Visual Studio. The document outlines Roslyn's SDK version, refactoring tools, and options for customization. It also lists some language features enabled by Roslyn like auto-property initializers, primary constructors, and exception filters. Links are provided to learn more about Roslyn on its CodePlex site and blogs.