A peer-reviewed journal contains articles written by experts that are reviewed by several other experts in the field before the article is published in the journal in order to insure the article’s quality. (The article is more likely to be scientifically valid, reach reasonable conclusions, etc.) In most cases the reviewers do not know who the author of the article is, so that the article succeeds or fails on its own merit, not the reputation of the expert.

Peer Review in Three Minutes 

The term scholarly or academic journals may also be used.

After you have carried out a search in Library search you can narrow your search to Peer Reviewed articles by using the Refine Your Search options on the left of the results screen or via the Advanced Search.

In most journal databases there is also an option to restrict your search to peer reviewed journals.