Most periodical publications fall into one of three basic types, which are described in detail in this guide: scholarly, trade, and popular. For academic research, your instructors will usually want you to use scholarly sources but knowing about the other types is valuable as well. In some disciplines, trade journals are very useful sources of information to stay current in the field.
For research assignments, a professor may require that you use articles from "scholarly" or "peer reviewed" journals. These are journals whose purpose is to disseminate new findings, results of studies, theories, etc.
Scholarly journals are written and edited by professors and researchers. Before publication, articles are reviewed by other researchers in the field of interest, hence the name "peer reviewed."
Many library databases allow you to limit your search results to peer reviewed articles.
Trade journals are written for "insiders" in a particular industry. Reviews are done by a staff editor.
Popular publications include news, feature stories, opinion/editorial pieces, etc. They are meant to inform and entertain. Minimal review by staff editor.