Peer review is a process in which a proposed publication is examined by people who are experts in the field which the publication concerns. These experts review the piece to look for errors and problems, determining whether or not the piece should be accepted for publication, grant money, awards, and other benefits. This process most commonly takes place in the sciences, where peer review is a cornerstone, although academics in fields like history may also put their work through a similar process.
This process is designed to catch errors, flaws, and issues with pieces which their authors may have missed. It assumes that everyone makes mistakes, sometimes fundamental ones, and that the benefit of a second pair of eyes can be extremely useful. Peer review is also used to ensure that pieces conform with generally accepted views and standards in the community, although it is not used to detect fraud, plagiarism, and other acts of dishonesty on the part of the author, with the review panel assuming that the author's intentions are honorable.
In many cases, peer review is anonymous, which means that when a piece is submitted, the author has no control over who is on the review panel, and he or she is not given the names of the people on the panel. Sometimes, the author's identity is obscured as well, to avoid bias on the part of the panel. Open review, in which the names of all parties involved are freely exchanged, has been growing in popularity.
Peer-reviewed publications tend to be viewed as more respectable and credible, both because they have been reviewed for errors, and because submission to peer reviewers suggests that an author welcomes insight and criticism from the community. Many scientific magazines and publications only accept pieces which have been peer reviewed, and some maintain their own panels reviewers.
The major flaw in this system is that it tends to be slow, and can delay publication for months or years, even when the information is of great interest or critical importance. It can also be difficult to find qualified reviewers, especially for works in esoteric, obscure, or cross-disciplinary fields. If a publication is being written by the premier specialist in a very small field, for example, it can be hard to find someone who would be appropriate for peer reviewing, let alone a panel of readers who can examine and discuss the piece.
When a submission is peer reviewed, there are usually four possible outcomes. The first and best is an acceptance without qualifications, meaning that the piece is deemed more or less perfect. The second is an acceptance with caveats, meaning that the author must make revisions for the piece to be accepted. Next is a rejection with an encouragement to revise and resubmit, suggesting that the work has merit, but the piece was too flawed to consider for publication. Finally, a piece can be simply rejected with comment.