Sometimes your professor might qualify an assignment with instructions to use only scholarly sources. This is especially true when working with articles. The terms “peer-reviewed” and “refereed” mean that a panel of distinguished peers in a particular field have read the articles contained in a particular journal in that field and have decided that they are of high scholarship and are supported by appropriate research.
The Library has a handout that helps to better illustrate the differences between “scholarly” and “popular” sources. Check it out at: