What's the difference between periodicals, journals and magazines?

A periodical is any publication that comes out regularly or occasionally (periodically).  Sports Illustrated, The Journal of Anthropological Research, The World Almanac, The Wall Street Journal and the phone book are all periodicals.  

A magazine is a periodical with a popular focus, i.e. aimed at the general public, and containing news, personal narratives, and opinion. Articles are often written by professional writers with or without expertise in the subject; they contain "secondary" discussion of events, usually with little documentation (e.g. footnotes). Magazines use vocabulary understandable to most people, and often have lots of eye-catching illustrations. Time, Newsweek, U.S. News & World Report, and Psychology Today are magazines

An academic journal is a scholarly periodical aimed at specialists and researchers. Articles are generally written by experts in the subject, using more technical language. They contain original research, conclusions based on data, footnotes or endnotes, and often an abstract or bibliography. Some academic journals are peer-reviewed, but not all.  The Journal of Physical Chemistry, The Chaucer Review, The Milbank Quarterly, and Labor History are examples of journals.

It's important to understand the differences between journals and magazines. Magazines are not necessarily bad or low quality (nor are journals necessarily high quality) -- they simply aren't designed to support most upper-level academic research. This is because they don't document their sources of information, and they generally lack the depth of scholarly journals.

For a more in-depth look at the differences between varying types of periodicals, and how to tell if an academic journal is peer-reviewed, view the files below.

For help with peer-reviewed articles,

1.  When searching for articles in databases, limit your search results to peer-reviewed content.  Most databases provide this option, usually by checking a box on the search or advanced search page:
 

You can look up the journal in Ulrich's Periodicals Directory (shelved downstairs at - Z6941 .U5).  The journal title index in v. 4 will show a black arrowhead by any title that is peer-reviewed.