Peer-reviewed or refereed journal: A periodical or other serial which contains scholarly articles. Manuscripts are refereed (evaluated) by at least one subject specialist in addition to the editor before being accepted for publication. The editorial board ensures a better chance that the final product will be a contribution to knowledge. It is also referred to as a “scholarly journal” or an “academic journal.” Usually includes footnotes and/or bibliography.  Articles often begin with an abstract.  To see if a specific journal title is peer-reviewed, check the Ulrich's Periodicals Directory database.  Examples of peer-reviewed journals are:

American Journal of Botany
Annals of Mathematics
Feminist Studies
Hispanic American Historical Review
Publication of the Modern Language Association (PMLA)
Womens Studies Quarterly

By comparison, popular magazines are periodicals for general reading, containing articles on various subjects by different authors.  The authors are not necessarily experts on the subjects in their articles.  Examples of popular magazines are:

New Scientist
Smithsonian
Ms.
Opera News
National Geographic
Art in America
New Yorker
Newsweek

More definitions--more examples!

View a chart summary of the major differences among the various types of serials.