Active Directory user schema has enough properties/attributes to cover most user profile information, but in some cases , we might need to extend this schema to add our own custom attributes. Microsoft Active Directory provides this capability to customize the user schema at various domain/forest hierarchy levels. The below article was tremendously helpful for us to achieve this. Thanks a lot Kurt Hudson.
Unique X.500 Object Id: is an unique object identifier for an attribute. This is NOT auto-generated when extending user schema, we need to come up with one or use this script to generate one. For more information, please check Obtaining an Object Identifier from Microsoft