Just would like to make clear, I cannot find straight answer. C# is general specification of this language done by MS, while Visual C# is implementation of this language, ag
You can say that Visual C# is the tool that is part of Visual Studio, provided my Microsoft used to create programs in the C# language.
There is the ECMA-334 C# Language specification, that defines the language.
There are other tools to create programs in C#, like SharpDevelop or MonoDevelop.