Overview#Relative Distinguished Name (RDN), is a single component within a Distinguished Name.
Relative Distinguished Name is comprised of one or more name-value pairs, in which the name and the value are separated by an equal sign (e.g., for an RDN of "uid=ann", the name is "uid" and the value is "ann"), and if there are multiple name-value pairs then they should be separated by plus signs (e.g., for an RDN of "cn=Jon Doe+employeeNumber=12345", the name-value pairs are "cn=John Doe" and "employeeNumber=12345").
In practice, Relative Distinguished Name containing multiple name-value pairs (called "Multi-Valued RDNs") are rare, but they can be useful at times when either there is no unique attribute in the entry or you want to ensure that the entry's Distinguished Name contains some useful identifying information.
For Example, in a DN of "uid=john.doe,ou=People,dc=example,dc=com", the RDN would be "uid=john.doe". The attribute values specified in an entry's RDN must be contained in that entry, so the entry "uid=john.doe,ou=People,dc=example,dc=com" must have a "uid" value of "john.doe" and the Naming Attribute is "uid".