This following LibGuide from Oregon State University gives a great detailed explanation about Peer Reviewed Articles: https://guides.library.oregonstate.edu/c.php?g=285842&p=1905633

If your professor is requiring research sources be from a peer-reviewed journal, be sure to click the box "Peer-Reviewed Journals Only" when searching for articles. You can find that option by clicking on the "Advanced Search" link found in scholarly databases. That way, your search will only return articles found in peer-reviewed journals.