Active Directory naming context (NC) or directory partition, is a logical portion of the Microsoft's Active Directory (AD).
Active Directory can support tens of millions of objects. To scale up those objects, the Active Directory database is divided up into partitions for replication and administration. Each logical partition replicates its changes separately among domain controllers in the forest.
Some directory partitions store forest wide configuration information and schema information; other directory partitions store information specific to individual domains, such as users, groups, and organizational units.
By default, the Active Directory Domain Service contains the following naming contexts: