Every industry in the United States is assigned a North American Industry Classification System (NAICS) code. NAICS codes are used for a variety of purposes, from access to business loans to applying for federal contracts
A business may have a primary NAICS code (the code that best fits the business and describes its primary activities) and a secondary, or even third code (meaning the business also has characteristics of additional industries).
Many business databases will assign NAICS codes to articles and company profiles. Below is an example from Business Source Complete where a NAICS code is assigned to an article. Once you know the NAICS code for your company's industry, you can also search business databases by NAICS code.
There is a second older classification system known as Standard Industrial Classification (SIC) code that is still used but has been replaced, for most purposes, by the NAICS code.