This functionality allows the user to view two apps simultaneously by layering one application in a smaller window on top of another app. (androidheadlines.com)
Android O users will see a small dot that appears over top of their app icons with active notifications. (androidauthority.com)
While these can certainly be useful, it would still be nice if this permission were taken literally and we could actually draw on top of apps. (android.gadgethacks.com)