It is much easier to do research in the business world when you know the NAICS code for the company you're researching. What's a NAICS code? NAICS stands for North American Industry Classification System and was developed by the US, Mexico, and Canada to assign each industry a unique classification. NAICS codes replace the older SIC codes, which you may also see references to.
You can look up the NAICS code for the industry your company is classed in on the Census Bureau's NAICS page (look for the search box on the left that says 2007 NAICS search).
It may also be listed in other sources, such as Mergent, Business Source Complete or other business databases. These can be helpful if you are having trouble narrowing down which industry your company operates in, but be aware that the Census Bureau's page is the ultimate source if there is a discrepancy.