NAICS and SIC codes are the two major systems governments & other entities use to classify the activities of businesses to make it easier to collect, analyze & publish data about economic and industrial activity. Finding the codes that apply to your topic make it easier to research in business databases since much of the information is searchable by industry code.
Here are the differences between the two classification systems:
Both Standard Industrial Classification (SIC) and North American Industrial Classification System (NAICS) codes identify a firm's primary business activity. For example a firm with SIC 571 primarily sells retail furniture. A firm with NAICS 311 is primarily engaged in food manufacturing.These codes were developed by the federal government and are used by the U.S. Office of Management and Budget as well as many other national and international organizations.
In 1997, OMB adopted NAICS as its new industry classification system for U.S. business classification but many non-North American countries still use SIC codes so it's important to find both the NAICS and SIC codes that apply to your topic.