CNAM stands for Calling Name Delivery or Caller ID Name. CNAM is the service that provides the name of a caller, and is related to CLID (Caller ID / Caller Identification), which is the telephone number of the person calling you.
In some countries, CNAM (name) and CLID (number) is transmitted with the call, and in some it is not. For example, in the United States the CLID is transmitted with a phone call, but the CNAM is not, and the carrier of the person whom is called takes the CLID and looks up the CNAM in a database.
TrueCNAM provides a service that allows anyone to populate our database with their telephone number and the associated name they wish callers to see, and for anyone to query that information.
You may also want to see: How is TrueCNAM different?