Adaptive icon
Android's answer to every manufacturer wanting its own icon shape — the app ships two layers, the system does the cropping.
Before Android 8.0, each app shipped a finished square image, and the result was a home screen where Samsung's apps were round, your own square, and a few had their own irregular outlines. Adaptive icons split the image into foreground and background, both larger than the visible area, and let the launcher apply its mask.
The margin is also used for animation: the icon can parallax as you swipe and bounce when pressed. The price is that the artwork must survive aggressive cropping — anything outside the inner safe circle may vanish on some manufacturer's screen.