When you want to present some settings on an iPad, you sometimes don't want it displayed full screen, but instead in a smaller window. This can be done by supplying the UIModalPresentationStyle enum value "popover" when presenting the view.
https://developer.apple.com/documentation/uikit/uimodalpresentationstyle
Example:
https://blog.verslu.is/wp-content/uploads/2018/07/Screenshot-2018-07-11-10.08.21.png
NB: For me only "popover" is needed; not the other style choices.