NAICS – North American Industry Classification System
(6 digit number used to describe type of business activity)
www.census.gov/epcd/www/naics.html

DUNS – Data Universal Numbering System
(9 digit number issued by Dun & Bradstreet unique to each business)
 https://eupdate.dnb.com/requestoptions.asp?cm_re=Homepage*Resources*DUNSNumberLink