Xamarin is a set of tools and libraries for building cross-platform mobile apps on the .NET platform. Build native apps for iOS, Android, Windows, and macOS on a shared .NET codebase.
Xamarin apps are built with standard, native user interface controls. Apps not only look the way the end user expects, they behave that way too. Xamarin apps have access to the full spectrum of functionality exposed by the underlying platform and device, including platform-specific capabilities like iBeacons and Android Fragments. Xamarin apps leverage platform-specific hardware acceleration, and are compiled for native performance.