A process used in journals that publish Primary Articles where a submitted article is sent to two or more experts in the field for a blind evaluation (where the reviewers do not know the names of the researchers who wrote the article).
Note: the following content is directly quoted from the University Library Guides offered by the University Library at Jönköping University
Within academia it is common practice to inspect texts before publication, from student essays to scholarly journal articles. This review process differs based on the type of text and publication. The most comprehensive and esteemed version of review is called peer review.
Peer review is used by journals that are known as academic, scholarly or scientific. These journals have a board of referees (or reviewers) who are experts and experienced researchers within their respective field. They evaluate the quality of the submitted articles based on scientific rigor, content and language. Together with the journal editor, they also judge whether the article fits within the subject area of the journal. The result of the review determines if the article is accepted for publication, if the authors are encouraged to revise the text or if the article is rejected.
Publishing articles according to the peer review procedure is required for a journal to be considered scientific. In order to avoid bias, the author and referee of the article are blinded to one another, i.e. their identity is kept anonymous.
Journals with a peer review system may include either refereed articles exclusively or a mix of refereed and non-refereed articles. Non-refereed articles might include book reviews, debate articles or commentaries.