The Mono Project implements a runtime and a developer platform based on the ISO standards for the Common Language Infrastructure and the C# language.

Mono embraces and extends these standards: we have brought these APIs to multiple systems and we have created our own open source APIs, frameworks and tools that anyone can use.

The Mono Runtime runs applications that have been developed with C# and the Microsoft .NET platform on a variety of operating systems and architectures that span most Unix systems (including Linux and MacOS) to embedded systems like the iPhone, the Wii and Android.

Mono allows developers that are familiar with Microsoft .NET technologies to bring their software and their expertise to other systems. Mono has also created a significant set of technologies to help developers. Some were created over the years by the community, and some were created through Google's Summer of code. Additionally we have created technologies that take advantage of the host operating systems, some are Mono-specific (no equivalent in .NET), Unix-specific, X11-specific, Cocoa-specific or graphics specific.