Seamless integration
Xamarin provides seamless integration of Objective-C, Java and C++ libraries. This provides the ability to easily integrate with many third-party
code bases which are in Java, Objective-C or C++.
Robust Compile Time Checking
Xamarin provides powerful compile time checking. This will reduce the run time errors and in effect provide high quality applications.
Xamarin is a Microsoft-owned San Francisco, California-based software company founded in May 2011. It has a C#-shared codebase with which you can use
Xamarin tools to write native Android, iOS, and Windows apps with native user interfaces.You can also share code across multiple platforms, including
Windows and macOS.
Xamarin applications are compiled to
Xamarin delivers high performance with device-specific experiences using native APIs to create a good user interface and user experience.
      iOS - UIKit APIs to create user interface. Xamarin's iOS designer/ Xcode Storyboards can be used for designing the UI.
      Android - Android.Views to create user interface. Xamarin’s UI designer can be used for designing the UI.
      Windows - XAML for presentation layer, created in Visual Studio or Blend’s UI designer.
      Mac - Storyboards to be used for the presentation layer, created in Xcode.
      Xamarin.Forms - XAML to create user interfaces that can be shared across platforms.
Xamarin delivers high performance with device-specific experiences using native APIs to create a good user interface and user experience.
How Does Xamarin Work for Windows?
For Windows, C# is compiled to IL and executed by the built-in runtime, and does not require Xamarin tools.
Designing Windows applications following Xamarin’s guidance makes it simpler to re-use the code on iOS and Android.
Note that the Universal Windows Platform also has a .NET Native option which behaves similarly to Xamarin.iOS' AOT compilation.