I do not have a Mac so I can not use it anyways. But I was curious to what kind of code do they use. Is it like Java, c++ or what code do they use to develop the apps?

Objective-C which utilizes the Cocoa frameworks

Which is why it doesn't work on Windows...the Cocoa part...Cocoa is a bunch of runtimes, APIs and libraries underlying the Mac OS X developement layer.