AD Replicate

Reference:

https://blogs.msdn.microsoft.com/servergeeks/2014/07/12/ad-replication-process-overview/

Active Directory (AD) is a multi-master directory, meaning each directory services server—referred to as a domain controller—contains a fully readable and writeable copy of the directory services database.

Because all domain controllers can accept changes to the database, some method is needed to replicate those changes to other domain controllers, ensuring a consistent
database across all domain controllers.

This scheme is referred to as AD replication.