HOW TO CLOSE A WINDOW
To close a window just click on its CLOSE (red eXit) button, located in the top-left corner of the window. On a Microsoft Windows computer if the window belongs to a program that has multiple windows open, such as Microsoft Word 2010 or Paint, only the window whose CLOSE (red eXit) button you clicked on will be closed. It is only when you are closing the last window of that program will the entire program (software) terminate thereby releasing any resources (Graphics, Devices and so on) it was using. If a program only uses one window then that window will be closed whereby its associated program (software) will then be terminated and its resources released. On an Apple Mac computer the CLOSE (red eXit) button and windows in general work differently.
On an Apple Mac computer, depending on the application (program) and/or window in use, when you click on a window's CLOSE (red eXit) button it will either close that
window only whereby its associated application is still running in the background, for whatever reason(s), or it will close both the window and its associated application
together with any resources it may of been using such as Memory.
As an example; If you only have one Microsoft Word 2011 window open, displaying the contents of Document1 for example, and click on its window's CLOSE (red eXit) button only the Document1 window will be closed - Its associated application (Microsoft Word 2011) will still be running in the background just in case you decide to open another Microsoft Word 2011 document file, in which case that other document file will be displayed in a new window. And this is one of the main premises of the OS X (Mountain Lion) operating system; to keep applications running (open) in the background just in case they are needed again, which has advantages and disadvantages like anything else.
In the above example I am closing a Microsoft Word 2011 document file, called Document1, by clicking on its window's CLOSE (red eXit) button. When the Document1 window has closed the docked icon belonging to its associated application (Microsoft Word 2011) remains on the dock with its Indicator Light still glowing (Fig 1.1 below). This means the associated application (Microsoft Word 2011) is still open (running) in the background even though one or all of its document windows have been closed. The purpose of this is so that you can quickly open a new document file (window) and display its contents without having to relaunch the whole application again, from scratch. It just saves time not to keep closing down an application and relaunching it every time you need to open a new document file (window).
If a docked icon has no glowing indicator light underneath it, perhaps because the SHOW INDICATOR LIGHTS FOR OPEN APPLICATIONS setting (Dock preference) has been switched
off, you can still check whether or not the application is open (running) in the background by right clicking on its docked icon. If you see the QUIT menu-item it means
the application is still running in the background.
Clicking on the QUIT menu-item will first close any remaining opened windows associated with the open application before it then shuts down the actual application. So in Fig 1.3 below the open window displaying the contents of Document1 would be closed before the Microsoft Word 2011 application itself was shutdown. You know there is a window open that is displaying the contents of Document1 because Document1 is listed as a menu-item in the docked icon associated with Microsoft Word 2011. In Fig 1.2 there are no document windows open, so clicking on the QUIT menu-item would simply shutdown the Microsoft Word 2011 application only. And in Fig 1.4 there is no QUIT menu-item, only an OPEN menu-item, meaning the application called Microsoft Word 2011 is no longer running in the background and can therefore only be OPENed.
Just because you have closed an application's windows and quit (shutdown) the application itself does not always mean the complete application has been shutdown entirely. For example. The front-end application of your security software (i.e. Bitdefender), the part that lets you perform a virus scan for example, might of been shutdown with the QUIT menu-item so you can no longer use its front-end (i.e. its SCAN and UPDATE buttons) but that doesn't mean its back-end has been shutdown too. The back-end, the part you don't see on the screen, is normally a set of background tasks (not applications) that carry on protecting your computer (in the background) regardless of you OPENing or QUITting the front-end application (the application itself).
With an application such Contacts it opens, lets you enter/edit contact details and then quits altogether - So you open the Contacts application as normal, enter/edit contact details and then click on the application window's CLOSE (red eXit) button. The application (Contacts) then saves your entered/edited contact details (to the cloud for example), if need be, before closing its only window and quitting (shutting itself down completely). In other words, applications like Contacts can be shutdown completely by clicking on their CLOSE button.
So as you can gather; On an Apple Mac computer (OS X Mountain Lion) the closing of a window can also mean the shutting down of its entire application (i.e. Contacts), just a part of its application (i.e. Bitdefender) or simply the closing down of the selected window only.