These are part of a directory service or such. Both Active Directory and LDAP use these types of fields, and in Outlook/Exchange you can find something similar in the list of alternative addresses for a e-mail.
Quoting below from: Stack Overflow 
https://stackoverflow.com/questions/18756688/what-are-cn-ou-dc-in-an-ldap-search

• CN = Common Name
• OU = Organizational Unit
• DC = Domain Component

These are all parts of the X.500 Directory Specification, which defines nodes in a LDAP directory.