Anchor: Anchor is the visual component of the app where the notifications surface on the interface. To put it simply, this is the component on which the user will see the notification indicator/badge. Note that anchors are not necessarily sources of notifications, but only the component where the notification surfaces. An anchor could house notifications from multiple sources or just one. Think of it like this, sources are more on the architectural/informational level, but anchors are the visual component where you see the notification badges.