The .NET Framework compiles all .NET languages (like VB.NET, Visual C++.NET and Visual C#.NET) into Microsoft Intermediate Language (MSIL) using MSIL compiler. Remember we said that high-level languages use the compiler to compile the code into the operating system machine code and only this operating system will understand that code, but when we are compiling .NET code into MSIL code not specific to any operating system, we still need one more step. We need to compile MSIL code into the operating system specific Machine Code, and this is the job of Just-In-Time (JIT) compiler. .NET Framework use the JIT compiler to compile the Microsoft Intermediate Language code into Machine Code specific to the operating system, and now .NET applications can run on this operating system. So we have two steps: first we compile our C# code to MSIL code (which is not specific to any operating system and it’s specific to .NET Framework and only the .NET Framework can understand MSIL Code); after that we will use the JIT Compiler to Compile MSIL Code into the Machine Code.
Why are there two steps when we can have just one?
There are a number of reasons for compiling .NET applications in two steps and now we will know some of them.
All .NET languages’ code compile first to MSIL code (this is called ‘Language Interoperability’) which is specific to .NET, I mean that .NET Framework understands MSIL code and not the operating system. For example, imagine that we are working in the same company and you are Visual C#.NET programmer, other developers work with Visual C++.NET and I’m working with Visual Basic.NET. Because all these different languages’ code will compile to MSIL (as a first step), we can work together in the same project and every one of us will still work with his favorite programming language, and there is no need to learn the other languages. After we finish the project, Visual Studio.NET will compile the code to MSIL Code from the three languages after that JIT compiler will be used to compile the code to the Machine Code. If MSIL does not exist, then we can’t work together because every programming language’s compiler will not understand the other programming language code. But MSIL compiler understands all .NET languages code.
They call JIT compiler Just-In-Time compiler because it compiles the MSIL Code only when it needs to. MSIL Code compiles and saves to a file in the disk and, when we need to run the application, JIT will do its job so it’s just in time. JIT compiler is specific to the operating system and the platform, so to compile C# code on Windows NT2000 platform you need a specific JIT compiler. If you want to compile the code on another platform (like UNIX), you will need another JIT compiler specially created for that platform.
The above details are about the .Net Compiler
And It's supported(developing software) languages are list outed in the following link...
http://www.startvbdotnet.com/dotnet/languages.aspx