Azure DNS zones provides a fully-managed DNS zone hosting service. Unlike most Azure services the DNS service is global, replicated across regions by default.
Alias records allow referencing Azure resources from a DNS zone as opposed to directly specifying addresses, helping to contextualise references and avoid dangling references as resources change. They can be created for
CNAME resource records.
Note that there's a limit of 20 alias records per target resource, presumably due to storage limitations.
Private DNS Zones
Private DNS zones provide the same functionality as public DNS zones within linked virtual networks, specified via private DNS zone links.