There are several types of window including Folder Windows, Application Windows and Document Windows. 

•	When you open a folder in My Computer, the contents of the folder are displayed in a folder window on the Desktop.

•	When you start an application such as Microsoft Word or Excel an application window opens on the Desktop. 

•	A document window containing your working data appears inside an application window.

Each window on the Desktop has a Title bar at the top. This gives the name of the application or folder.

You can have several application and folder windows open on the Desktop at the same time.  Only one window can be active at a time.  The active window is always on top.