Scholarly sources contribute a great deal to the overall quality of papers because of their level of authority and evident credibility. Use of scholarly sources is an expected attribute of academic course work.
General attributes:
Popular sources can appear in magazines and newspapers. Information in popular sources can help you answer simple who, what, when, and where questions. Depending on the assignment, they can be essential for finding information about current events or issues. Popular sources range from research-oriented [but lacking complete citations to sources] to special interest, agenda-driven publications.
General attributes
Trade publications intend to share general news, trends, and opinions among practitioners in a certain industry or profession. Although generally written by experts, they are not considered scholarly because they are not peer-reviewed and do not focus on advancing new knowledge discovery or reporting research results.
Primary, Secondary & Tertiary Sources. Written by Ward Saylor & Helen Hooper for Information and Research Support, within the Information Services program of the Academic Support Division at James Cook University, July, 2000.
http://cms.jcu.edu.au/libcomp/assist/guides/azguides/JCUPRD_030412
Adapted from: https://libguides.usc.edu/writingguide/scholarly