Thanks to the University of Delaware Library for the infographic!
Journals, magazines, and newspapers can be divided into four basic categories (ranked here from most reliable to least reliable):
1. Scholarly
2. General Interest / Substantive News
3. Popular
4. Sensational
Think about it - if you were preparing a presentation on political parties, would you trust The Journal of Political Science or the local supermarket tabloid with aliens from Mars on the cover? That's the difference between scholarly and sensational!
SCHOLARLY journal articles are written by academic researchers. Often scholarly journals require articles to be reviewed by other experts or scholars in the same field who must agree that the article in question meets the standards of that profession in a proces called PEER REVIEW. This ensures that the content of the article is as valid and reliable as possible.
So how do you tell if a journal is scholarly?
(More information on the four basic categories can be found here from Cornell University Library.)