Some organizations (mainly business brokers and investment bankers) use industry codes to classify their listings. We support two types of industry codes: Standard Industrial Classification (SIC) codes and North American Industrial Classification System (NAICS) codes. Go here for more information about NAICS codes: https://en.wikipedia.org/wiki/North_American_Industry_Classification_System. Go here for more information about SIC codes: https://en.wikipedia.org/wiki/Standard_Industrial_Classification