What is the difference between a journal, a periodical, a magazine, and a trade journal? Is there a difference between an academic journal, a peer-reviewed journal, and a scholarly journal?
The broadest term is periodical. Simply, a periodical is anything that comes out periodically. That is, a version is released at regular intervals. Magazines, newspapers, and journals are all periodicals. They may come out daily, weekly, monthly, quarterly or annually, but new issues are released on a fixed schedule.
Journals, trade journals, and magazines are intended for three different audiences.
Magazines are for the general reader. If it’s in a book store, or found on a newsstand, it’s probably a magazine. Magazines typically have advertisements for popular consumer products like cars, cola, perfume, electronics, etc. They are often more focused on entertainment and light news than substantive research.
Trade journals are created for particular professions, or trades. Each profession generally has several trade journals with information mostly of interest only to people in that profession. They also have advertisements directed to that profession. For example, a trade journal for librarians might have an article on the cost of databases and advertisements for library shelving.
Academic journals, peer-reviewed journals, and scholarly journals often are synonymous. While there are scholars who are not academics, and academics who are not scholars, most of the scholarship produced is produced by academics (professors and graduate students). Scholarly/academic journals have a unique way of deciding what gets published and what doesn’t. While trade journals and magazines typically depend on editors to determine what gets published and what doesn’t, scholarly journals depend on the peer review process.
When an academic produces research and writes a paper/article about it he or she sends it to a scholarly journal. The editor of that journal removes the name from that research article and sends it to experts in the field to review. Since the person submitting the paper or article is also presumed to be an expert, these other experts are his or her peers. Hence the name ‘peer-reviewed.’ These peers read the research article and then recommend to the editor whether the article contributes significantly to the body of knowledge. If they approve of the article then it gets published. If they do not then it gets rejected.
The process is kept anonymous so that articles are not accepted or rejected based on personal likes or dislikes. The peer reviewers are to focus solely on the quality of the research and argument presented in the article submitted for publication.
The peer-review process isn’t perfect, but it’s the best way scientists, scholars, and other researchers have developed to ensure high-quality information. This is why your professors often ask you to focus on peer-reviewed literature. This is typically the most rigorous and highest quality research available.
UPDATE: Check out this video from Virginia Commonwealth University VCU Libraries on the differences between scholarly and non-scholarly sources —
Or, check out this page about Distinguishing Scholarly Journals from Other Periodicals from Cornell University Library.