NAICS (North American Industry Classification System) is used to classify a business' primary activity. It replaced SIC (Standard Industry Classification) in 1997.
For further business information regarding NAICS, you can access the following URL
Your firm was chosen from a scientifically selected sample of businesses. Taking a sample is less costly than contacting every business in the country. Smaller firms selected for the sample represent other similar businesses.
The sample is revised approximately every five years in order to relieve most firms from the burden of continually reporting. While the largest firms continue to be canvassed, most of the small and medium sized firms are not re-selected.
16. I'm a very small business. Why do you want information from me?
Taken together, small businesses have a real impact on the economy. Your firm was chosen from a scientifically selected sample of businesses and represents many other small businesses like yours.