No difference, only they are different functions (and "void" must be lo-case; you code won't format) and "main" is not the entry point of executable assembly by default.
It's important to know, that
the entry point does not have to be "Main". It can be any static method with on of the required signatures (
http://www.csharphelp.com/2006/08/entry-point-in-c-program/[
^]). If you are using Visual Studio, you can go to project's property and change the class where the entry point is supposed to be.
—SA