When we compile the .NET programming language code, the output of compiler is not executable code instead it generates special type of Pseudocode called as Microsoft Intermediate Language(MSIL). It can also referred as Intermediate Language (IL) or Common Intermediate Language (CIL).
When we run the program, Common Language Runtime(CLR) will translate MSIL code to executable code. CLR will covert MSIL code from any of .NET language.