Scholarly v. Popular
A scholarly publication is one in which the content is written by experts in a particular field of study - generally for the purpose of sharing original research or analyzing others' findings. Scholarly work will thoroughly cite all source materials used and is usually subject to "peer review" prior to publication.
Popular Sources aim to inform a wide array of readers about issues of interest and are much more informal in tone and scope. Examples include general news, business and entertainment publications such as Time Magazine, Business Weekly, Vanity Fair.
Note, special interest publications which are not specifically written for an academic audience are also considered "popular" i.e., National Geographic, Scientific American, Psychology Today.