Peer review is a practice in which an article proposed for publication is reviewed by a group of experts in the same field as the article to establish that it meets established standards for scholarly research.
Many databases include a checkbox that allows you to limit search results to peer reviewed items. Sometimes it appears in the area below the basic search box. If it isn't there, look at the search options available with the advanced search.
Another way to determine if an article is Peer Reviewed or Scholarly, is to search for the title of the journal which published the article in: Ulrichsweb
The Referee Shirt icon indicates the journal is refereed or peer reviewed.