A window is a rectangular area of the screen, usually with a border all around and a title bar at the top. You can think of a window as a screen within the screen. Each window displays an application, allowing you to to have more than one application visible, and work on more than one task at a time. You can also think of windows as pieces of paper on your desktop: they can overlap, or be side by side, for example.
You can control a window's position of the screen, as well as its size. You can control which windows overlap other windows, so the one you want to work with is completely visible. For more about moving and resizing windows, see Section 2.3.2 ― Manipulating Windows.
Each window is not necessarily a different application. An application usually has one main window, and may open additional windows at the request of the user.
The rest of this section describe the different types of windows and how you can interact with them.