This is the main zone and has a read/write copy of the zone data. All changes to the zone are made in the primary zone and are replicated to the secondary zones.
The zone data is stored in a text file located in this folder c:\windows\system32\DNS on the Windows server running DNS.
A secondary Zone is a read-only copy of the primary zone. This zone cannot process updates and can only retrieve updates from the primary zone. This zone can answer DNS name resolution queries from client’s nodes, this helps reduce the workload on the primary zone. Secondary zones cannot be active directory integrated.
Stub zones are like a secondary zone but only stores partial zone data. These zones are useful to help reduce zone transfers by passing the requests to authoritative servers. These zones only contain the SOA, NS and A records.