Active Directory Roles in Windows Server 2012
Active Directory Directory Service [AD DS]
A centralized store of information about network objects, including user and computer accounts. Used for authentication and authorization
Active Directory [AD CS]
Allows you to deploy certification authorities and related role services.
Provides web single sign-on (SSO) and secured identify federation support.
Active Directory Lightweight Directory Services [AD LDS]
Supports storage of application-specific data for directory-aware applications that do not require the full infrastructure of AD DS
Active Directory Rights Management Services [AD RMS]
Allows you to apply rights management policies to prevent unauthorized access to sensitive documents