Eclipse "crossGCC"

I just downloaded the Eclipse IDE for C/C++ (on Window 7) and trying to create a simple new project. In the tool chains there are "Cross GCC", "Cygwin GCC" and "Microsoft Visual C++".

I never heard of the "Cross GCC" before. What is the different between "Cross GCC" and "CygwinGCC" and the normal "GCC"?

--ABS