I was recently asked what the difference between CIL and MSIL is…   the short answer is not much.  They both describe the underlying CPU-independent instruction set the CLR executes after a high level language (C#, VB, C++, Python, Ruby, Pascal, etc) has compiled your source code.  The difference between them is the exact version you are referring to.

 

CIL -  Common Intermediate Language  - is the term used in the International Standard.  

MSIL -  Microsoft Intermediate Language   - is the product term for the Microsoft implementation of that standard.

 

Clear as mud?