A scholarly journal is a periodical publication which contains articles written by scholars and researchers. Before articles are published in these journals, they are judged for quality by a editorial board using a "peer review" process. If the article meets the standards of the scholarly journal, then it is published.
You can locate scholarly journals in Smart Search and most of the CMU Libraries databases. Many databases provide an option on the search screen that indicates "scholarly" or "peer review", and many allow you to limit your results to Scholarly Journals or Academic Journals.
Take a look at the resources linked below for a more detailed explanation about the differences between scholarly articles and popular articles, and see how to find scholarly articles in databases.