What is an IL or MSIL or CIL?

 All programs targeted to .NET are converted to MSIL (Microsoft Intermediate Language). MSIL is the output of language compilers in .NET. MSIL is then converted to native code by JIT (Just in Time Compiler) of the CLR and then native code is run by CLR.
As every program is ultimately converted to MSIL in .NET, the choice of language is pure personal. A program written in VB.NET and a program written in C# are both converted to MSIL. Then MSIL is converted to native code and run. So, whether we write program in C# or VB.NET at the end it is MSIL all that we get.