The North American Industry Classification System (NAICS, pronounced "nakes") is a system for organizing data on industries and companies for standardized reporting. NAICS was implemented in 1997 and was developed by the United States, Canada, and Mexico.
The system assigns different numerical codes to companies based on the type of products or services the company provides. Organizations with similar products or services are grouped together. NAICS was designed to for statistical purposes, but also makes business research and reporting easier. You can find more information about NAICS on the Census Bureau's NAICS FAQs.