Peer-review articles come from peer-reviewed journals. When an article goes through the process of peer review, the article is critiqued by experts in the field before publication. This process may also be called “refereed” or “juried."
Many databases in the library's collection have a filter or limiter option for peer review. Select that filter/limiter when searching to only receive results from peer-reviewed publications (The filter/limiter may be in the advanced settings of the database so look for this option there too.). But remember not everything in a peer-reviewed journal is actually peer-reviewed, opinion pieces, letters to the editor, letters from the editor, etc. are not peer-reviewed.
NOTE: Google Scholar does not provide a limiter for peer-reviewed journal articles.
You can also do a quick web search for the journal title. Look at the journal's website (usually in the "about" section) and read the information about the journal. If it is peer-reviewed, the website will state this.