Those are notifications. Pull down from the top of your screen to see them. When you act on them the notification will go away.
Yes. That is true there are exceptions.Actually I can think of a couple of exceptions...Adguard which activates VPN runs in the background so the only way to "clear" it is to disconnect it. And I believe any temperature icon for the weather would be running in the background. Others, such as Slacker Radio are in the notification tray and can be swiped away or left there for easy access later, but it isn't actually running as far as I know.