It's an extension of the basic caller ID function, which typically shows only the phone number. 

• Name Display: CNAM allows the recipient of a call to see the caller's name on their phone's display screen. This name is usually associated with the billing account of the calling number.

• Enhanced Caller Identification: By providing the name of the caller, CNAM offers an additional layer of identification, which is particularly useful for determining whether to answer an unknown call.

• Use in Business and Personal Communications: CNAM is valuable for both personal and business phone systems, as it helps users quickly identify incoming calls from clients, customers, or personal contacts.

• Accuracy and Variability: The accuracy of CNAM information can vary, as it depends on the data provided by the originating phone carrier and the completeness of the CNAM database. In some cases, outdated or incorrect information might be displayed.

CNAM enhances the caller ID experience by providing more detailed information about the incoming caller, thereby improving call management and adding a level of security for the recipient.