Peer reviewed sources are those that have been vetted by scholars in a given field. For example, before a peer reviewed, or refereed, journal will publish an article, it is first sent to a handful of scholars in that field to conduct a blind review. They will often return the article with suggestions for improvement before recommending that the journal publish the article. This is considerably different than popular magazines and other sources that do not employ such rigorous publishing standards. The result is a higher level of scholarship than might otherwise be published.

Look for these structure elements when you're evaluating an article to confirm that it's peer reviewed:

Article Title

Usually rather lengthy, including technical terms and methodologies.

Author(s) & their Credentials

In addition to their names, you may also see authors' credentials - where they work/teach, their degrees, contact information etc. This information is included to help establish their authority.

Abstract

A brief summary of the article - often divided into the same sections as the article text. Readers use abstracts to quickly determine if the article will help meet their information needs. 

Article Text

The actual text of the article is usually divided into sections with headings: introduction, literature review, methods, results, discussion and conclusion. There are frequently also charts and other visual representations of data.  

References 

You'll find in-text or footnotes throughout an academic article, and a length list of corresponding citations at the end of a scholarly article. These references are connect a scholarly article to the larger field of research and demonstrate the evidence and other research that the work is based on. References are also a great place to look for additional sources on your topic.

Try the NCSU Library's interactive Anatomy of a Scholarly Article.