The two industry classification systems you will come across most often are NAICS and SIC. Both are hierarchical, organized by broad industry categories, each divided into more specific industries.
Trade publications focus on one industry and provide in-depth information on trends, new products and other topics of interest to people working in that industry.
TIP: In EBSCO-hosted databases (Business Source Complete, Academic Search Complete, etc.), limit your search to Trade Publication under Publication Type.