如何使用Android XML Layout？

The purpose of the XML layout is confusing for me, having only worked with UI in Visual Studio with the drag-drop xml layout and C# code-behind. Should I be creating a separate xml layout for every screen (load, main, data) in my application? How do views associate with layouts? How do I reference the xml and use it in my code? I only know of the setContentView(xml layout) call. The purpose of the XML layout is confusing for