Peer Review is a process that journals use to ensure the articles they publish represent the best scholarship currently available. When an article is submitted to a peer reviewed journal, the editors send it out to other scholars in the same field (the author's peers) to get their opinion on the quality of the scholarship, its relevance to the field, its appropriateness for the journal, etc.
Publications that don't use peer review (Time, Sports Illustrated, Cosmopolitan) just rely on the judgment of the editors about whether to publish an article or not. That's why you can't count on them for solid, scientific scholarship.
Note: This is an entirely different concept from "Review Articles" (from Libraries at University of Texas-Austin).
Examples of Peer-Reviewed Journals:
Nature, the Lancet, the New England Journal of Medicine, Japanese Journal of Ornithology, Zoo Biology
How do I find these journal articles?
Use databases such as Science Direct and Academic Search Complete to find peer-reviewed periodical articles. Use the "Limits" box to limit your search to Peer-reviewed journals. CAUTION: you may not find much if you also limit to full-text. Try your search without limiting to full text and use Interlibrary Loan to obtain copies of the articles you need.
Biological Abstracts is the best database for peer-reviewed journal research in biology. Parkland does not have access to this database. You can go to U of I and use it on campus in any of the libraries.