The Directory Service Protocol that is utilized by AD DS is based on the Internet-standard Lightweight Directory Access Protocol defined by RFC-3377. LDAP allows queries and updates to take place in AD DS. Objects in an LDAP-compliant directory must be uniquely identified by a naming path to the object. These naming paths take two forms: distinguished names and relative distinguished names.
Explaining Distinguished Names in AD
The distinguished name of an object in AD DS is represented by the entire naming path that the object occupies in AD DS. For example, the user named Brian McElhinney can be represented by the following distinguished name:
The CN component of the distinguished name is the common name, which defines an object within the directory. The OU portion is the organizational unit in which the object belongs. The DC components define the DNS name of the Active Directory domain.
Outlining Relative Distinguished Names
The relative distinguished name of an object is basically a truncated distinguished name that defines the object’s place within a set container. For example, take a look at the following object:
This object would have a relative distinguished name of OU=Sydney. The relative distinguished name in this case defines itself as an organizational unit within its current domain container.
Source of Information : Sams - Windows Server 2008 R2 Unleashed