There are many different types of information sources. Each is characterized by different elements and target audiences.
Non-scholarly sources inform and entertain the public or allow practitioners to share industry, practice, and production information
Examples: Newspapers, magazines, trade journals, popular books.
Scholarly sources disseminate research and academic discussion among professionals within disciplines; they are intended for university-level study and research, and are preferred when writing university-level essays.
Generally, non-scholarly sources do not examine a topic with the level of detail and sophistication that your professor expects. They are not authoritative (the authors are often not academics). They are written to entertain and broadly inform, rather than to advance a field of study. They may be acceptable for high school level essays, but they are not acceptable for university level essays.
Note: If an article is peer-reviewed/refereed. Books and Handbooks can be scholarly as well. The editors determine if a book is peer reviewed.