Answer: 

Industry codes have been developed over the years to provide a way to classify industries into categories and group firms of similar nature together. There are several major industry code systems: Standard Industrial Classification (SIC) and North American Industry Classification System (NAICS) were created an are maintained by the U.S. government. These can be searched on the Census website. GICS, produced by Standard & Poorís and MSCI, is used primarily by financial analysts.