The North American Industry Classification System (NAICS) is an industry classification system. It has a hierarchical structure, dividing the economy into 20 broad sectors. Within each of these sectors, economic activities are further organized into narrower categories. For example, this is a snapshot of the NAICS hierarchy for the Resorts industry:

• 72 Accommodation and food services
• 721 Accommodation services
• 7211 Traveller accommodation
• 72111 Hotels (except casino hotels) and motels
• 721113 Resorts 

The (721113) Resorts category is at the narrowest level of the hierarchy. The broad sector, in this case, is (72) Accommodation and food services. Within this sector, there are many categories and subcategories. NAICS codes may be used in some library databases to search for industry reports, company profiles, or to create lists of companies.