Stub Zone , Delegation and Conditional Forwarding

Stub Zones:
Stub Zones are rather like DNS Secondary zones. The similarity is that both Zones have a read only copy of the server that is authoritative for a child DNS domain. The difference is that Stub Zones have only 3 records, SOA, NS and A, whereas Secondary zones have a full set of A records. Finally, the logic is that you create the Stub Zone only in the Root domain and the Stub Zone then has three records for each child domain.A copy of the SOA record for the zone.Copies of NS records for all name servers authoritative for the zone. Copies of A records for all name servers authoritative for the zone
Incidentally, the A (Host) records in the Stub zone are referred to as 'glue' records.
The point of Stub Zones is to streamline administration, improve name resolution and possibly, reduce network traffic. Needless to say, Stub Zones are only needed in large complicated Forests, and are unnecessary if you only have one domain.
Delegation :The DNS infrastructure can be defined by its points of delegation. Beginning with the root of the DNS ("."), each zone administrator has the authority to delegate sub-zones to other responsible parties. Each sub-zone becomes another delegation point in the DNS infrastructure tree. In Essence Delegation Simply means that you have Delegated a Particular Zone.All the records for that Zone will be Maintained by the DNS Server you have Delegated to .The DNS Server you have Delegated to will be Autoritative for the Zone and will contain all the records for that Zone.
Conditional ForwardingConditional DNS forwarding is rather like taking a short cut. If I am in guybay.com and I am running DNS and I want to contact quickgear.org, then I could go via the root ' . ' domain, then the org server, then quckgear.org. Or, provided I knew the server IP address in quickgear.org, I could set up conditional forwarding and so take a shortcut.