Microsoft Intermediate Language (MSIL)

MSIL is the only language the .NET CLR can understand. Every .NET language compiler, in the end, spits out MSIL code. Then, when the application runs, the CLR's Just-In-Time (JIT) compiler converts it to machine code on the fly.

• Language independence: As long as you can write a compiler for your language that produces valid MSIL, you can integrate it into the .NET world.
• Hardware independence: Theoretically .NET could be ported to other platforms like Linux or the Macintosh, in the same way Java is. All you need is a CLR implemented on the new platform that can convert MSIL to the native machine code.
• Built-in low-level features: Because there's a single point of entry for all code, regardless of the language it was developed in, features that were formerly a part of the language itself can be implemented at the CLR level. All code that's run through the CLR is called managed code because features like security, type safety, garbage collection, multithreading, multi-language projects and easy deployment are managed at that level.