Account Domain is a type of domain in Windows Server Systems in an enterprise containing global user accounts and global group accounts throughout. Account domains simplify account administration by centralizing administration to a single domain.

Account domain authentication
User authentication in account domain passing through all domain controllers.
How it works
An account domain is often a master domain too when used in a single master domain model implementation of Windows NT. The account domain contains user accounts for every user in the enterprise and is usually located at corporate headquarters.
Servers and workstations at company branch offices belong to other domains called resource domains. Users at branch offices who want to log on to the network must log on to the account domain, even though their workstations are located within a resource domain.
For this scenario to work, a trust relationship must be established so that each resource domain trusts the account domain. In this way, all user accounts can be centralized in the account domain, which eases account management for administrators located at headquarters.