Xamarin is a cross-platform mobile development framework that allows developers to create mobile apps using C# and Visual Studio, taking advantage of native APIs and tooling. It provides a shared code base for business logic and UI, with options for Xamarin Native and Xamarin.Forms approaches. The framework supports both C# and F# programming languages and offers day 1 support for new OS releases and features. With the right tools and knowledge, developers can create mobile apps for Android, iOS, and other platforms using Xamarin. The framework also includes a suite of tools and resources to help developers get started with building their first app.