IL:

IL is a intermediate language, which is created when you compile the .net program. This is also a object oriented language. This makes cross language inheritance.

c#:

C# is a new OOPs language which is developed by Microsoft. This language gives flexibility, mordern, easy to use.

c# is one of the programming language defined as "Type safe version of c with oops" developed by Microsoft corporation.

IL(Intermediate Language) is a code which can be converted by .net to support the cross language support.

(That is whatever the language like c#, vb, c++,j# is used to program in .net that code is converted into IL which is common for all .net platform supporting languages before the execution, it supports the cross language support in .net platform)