Here are some screen shots of apps opened via the Multi-Window Panel:
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I Google Image searched for a random price list to use for this example and then used the CALC app on top to see the difference between two of the packages on the list. The white circle at the top of the calculator app window is what you use to drag the window wherever you want it, and if you tap on the circle, you get a options to minimize it, maximize it, close it, and another option.
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You can see the CALC app icon after I minimized the app. You can drag this floating icon anywhere.
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Here, I am watching a video of my dog playing in the MX Player app via the Multi-Window Panel. The volume keys work to adjust the sound for the video from loudest to muted.
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It ain't called MULTI-Window for nothin'! Here, I have the MX Player app minimized (blue icon with white triangle) while I have CALC, Fraction, and Phone placed around the screen. I would probably never actually use it like this, but it can be done.
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Lastly, here are all those apps minimized to icons and placed on the edge of the screen in an overlapping lineup. You can place them anywhere, but the only annoying thing is your placement isn't saved if you open the app up to a window or maximized full screen, so if you minimize it to an icon again, you have to re-place it where you want it. The Facebook Messenger floating icons remember where they were placed, so I am sure it is something Samsung could implement, they just haven't. And if you have the setting activated, if you maximize one of your apps, just drag your finger down diagonally from the upper left corner to get the app back to a window (as you can do with any app that supports the multi-window feature, even if you didn't open it from the panel).