Complex sentence: Xamarin is a San Francisco, California based software company created in May 2011 by the engineers that created Mono, MonoTouch and Mono for Android which are cross-platform implementations of the Common Language Infrastructure (CLI) and Common Language Specifications (often called Microsoft.NET).
Split into simpler sentences: Xamarin is a San Francisco, California based software company created in May 2011. The company was created by the engineers that created Mono, MonoTouch and Mono for Android which are cross-platform implementations of the Common Language Infrastructure (CLI) and Common Language Specifications (often called Microsoft.NET).