Explanation/Reference:
Explanation:
http://technet.microsoft.com/en-us/library/cc771898.aspx
When a zone that this DNS server hosts is a secondary zone, this DNS server is a secondary source for information about this zone. The zone at this server must be obtained from another remote DNS server computer that also hosts the zone.
With secondary, you have ability to resolve records from the other domain even if its DNS servers are temporarily unavailable.
While secondary zones contain copies of all the resource records in the corresponding zone on the master name server, stub zones contain only three kinds of resource records:
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.

References:
http://www.windowsnetworking.com/articles-tutorials/windows-2003/DNS_Stub_Zones.html
http://technet.microsoft.com/en-us/library/cc771898.aspx
http://redmondmag.com/Articles/2004/01/01/The-Long-and-Short-of-Stub-Zones.aspx?Page=2