Xamarin is a tool used for cross-platform mobile app development that allows engineers to share up to 90 percent of code across major platforms.

C# language. Xamarin uses a single language, C#, to create apps for all mobile platforms. Unlike interpreted solutions, Xamarin is natively compiled, which makes it a go-to option for building high-performance apps with native look and feel.

Based on .NET framework. C# is a mature language with strong safety-typing that prevents code from unexpected behavior. As C# is one of the .NET framework languages, it can be used with a number of useful .NET features such as Lambdas, LINQ, and Asynchronous programming (async/await).

Technically speaking, Xamarin uses C# and native libraries wrapped in the .Net layer for cross-platform app development. Such applications are often compared to native for both iOS and Android mobile development platforms in terms of performance and user experience. Additionally, Xamarin can leverage all native and the latest API access to utilize underlying platform capabilities in Xamarin apps such as ARKit on iOS or Android Multi-Window.