Often your professor will suggest that you use scholarly or peer-reviewed journal articles for your research project. However, it is not always easy to discern the difference between the three major article types: scholarly, trade, and popular.
There may be times when you should use only primary or secondary sources, but how do you know when to use one over the other? And what about tertiary sources? What are those?
For example, book reviews, editorial pieces, short news items, etc. do not count as "scholarly articles".
If you are unsure about an article you've found, check with a librarian or your professor.