In the .NET world IL, MSIL, and CIL all refer to the compiled output of .NET languages.
- IL - Intermediate Language
- MSIL - Microsoft Intermediate Language
- CIL - Common Intermediate Language
As a side note CIL isn’t able to be executed directly. Instead it relies on a second compiler to turn it into proper assembly code for the machine it is running on. There are currently three main CIL to Assembly compilers: Microsoft’s CLR (aka JIT), Microsoft’s NGEN pre-compiler and Xamarin’s Mono project (also a JIT).