Periodicals includes magazine articles, newspapers articles, journal articles etc. Journal articles are often scholarly or peer-reviewed.
What can help you determine if an article is from a peer-reviewed journal?
1) Database Filters/Tagging - often alert you to the source type
2) Article Structure - be aware of the article's characteristics often alerts you to the source type e.g. length, bibliography, tone
3) Tools like Ulrichs - look for a title, will indicate if it is peer reviewed check if it is peer reviewed status