Not all scholarly articles are peer reviewed. To find out if the article you are reading has been peer reviewed, look up the journal title in Ulrich's Serials Directory. The referee's shirt next to the title indicates that the journal is peer reviewed.
A peer reviewed journal may include articles like opinion pieces or editorials and book reviews. These articles may not be peer reviewed. When looking for peer reviewed research articles, be sure to look for elements of a scholarly research article (methods, discussion and results sections, bibliography).