The journals we refer to as "peer-reviewed journals" include some items that are not peer-reviewed, such as editorials, columns, news, etc. Only the scholarly or research articles are submitted for peer review.
Peer review is described in the Oxford English Dictionary Online as:
"The process by which an academic journal passes a paper submitted for publication to independent experts for comments on its suitability and worth; refereeing."
Because peer-reviewed journal articles have been reviewed and edited before publication, they are considered a highly credible source of information.
Use appropriate journal databases to increase your access to peer-reviewed journals:
These databases index the scientific literature, and cover most of the highly regarded life sciences journals. The majority of these journals are peer-reviewed.
There are several ways to check whether a journal uses peer review: