It’s common to have multiple DNS zones where one zone is a “vanity domain” for a “real” zone.
For example, if your main zone is mycompany.com, you may also purchase mycompany.io as a secondary zone. In this case, you want any records created in mycompany.com to also be available under mycompany.io — that is, www.mycompany.com and www.mycompany.io should point to the same place. Furthermore, as changes get made to the main mycompany.com zone, you want the changes to also be reflected in mycompany.io zone.
You could create the two zones and keep them manually in sync, but, we bet you have better things to spend your time on.
That’s why we cooked up a simpler solution called “Linked Zones“. Linked Zones allow you to create these vanity domains which point to the “real” (target) zones containing the records.