For conceptualizing different types of sources into a logical framework, consider them by the level at which they analyze a given topic.
This can be visualized as a three-tiered pyramid. At the base of the pyramid are the 'popular sources', or the information written for a general audience: newspapers, magazines, websites, blog posts, etc. They often provide an interesting window into a topic, but are not designed for in-depth analysis.
In the second tier are the 'trade publications', or the magazines written for people in a specific industry or occupation. These are glossy and visual like popular magazines, but their attention to certain issues is more focused. Trade publications are not scholarly, however.
The 'scholarly sources' occupy the third tier, and are written by experts in a field of study. These are typically journals and books from academic publishers. They are vetted for accuracy and originality, and provide the most in-depth analysis of an issue.
Scholarly Articles (aka Peer Reviewed/Refereed)