NAICS (rhymes with snakes), is the North American Industry Classification System. It is a 6-digit, hierarchical code that is used to classify "lines of business" for establishments for the purpose of collecting, analyzing, and publishing statistical data. NAICS codes are replacing the Standard Industrial Classification (SIC) system.
Many of the Library's company and industry databases allow you to search by NAICS or SIC code or by keyword and may allow you to browse by industry codes.
See the NAICS Main Page, which includes a browseable hierarchy/structure of codes and a keyword search.
Image captured from database 01/01/2014
Access industry, market and country research reports from such publishers as Datamonitor/MarketLine and others.