The following 3-minute video produced by Vanderbilt University's Peabody Library provides a good overview of the differences beween popular and scholarly periodicals.
Distinguishing Scholarly Journals from Other Periodicals
(Permission received from Research & Learning Services, Olin Library, Cornell University Library, Ithaca, NY to reproduce and adapt this guide for our own use.)
Scholarly, Trade, and Popular Journals (from the Ithaca College Library)
Comparison Chart: Scholarly (Academic) vs. Popular Articles (from the UC Davis Library)
Scholarly Journals, Trade Publications, and Popular Magazines (from ProQuest)