Administrative templates are the core elements that make up a GPO. Most settings available within an administrative template are used to configure a corresponding Registry value for the computer or a user account, usually defined within the HKEY_Local_Machine or the HKEY_Current_User Registry hive. Other settings are provided to run computer-based and user-based scripts and, in some instances, install or make software packages available to subsets of users or computers.
Administrative templates come in three basic types:
• ADM files for Windows 2000 Client and Server, Windows XP, and Windows Server 2003
• ADMX and ADML files for Windows Vista, Windows Server 2008 and later OSs
• Custom ADM, ADMX, and ADML ...