Here's a question that comes up sometimes, related to how a new window opens and behaves. In case you missed the Tech Tip in Optonews, click here:
Child vs. Popup
FYI, these terms "child" and "popup" are standard windowing terms. Here's more detail than you probably care to see from Microsoft.
To help you remember which one is which, it might help to think of the annoying Pop-up Ads you often see in browsers. They stay on top until you close them, like the Popup option in PAC Display.
Hope that helps!