In order to ensure the quality of articles published, articles submitted to scholarly journals go through a peer-review process before publication.
First, a scholar or group of scholars submits an article to a journal they'd like to publish in.
Second, the journal sends that article to several (generally three) other scholars who work in the same area for review.
Third, the peer-reviewers read the article and recommend either: publication, revision, or rejection.
If the peer-reviewers recommend publication, the article is published without changes. This is relatively rare.
If the peer-reviewers recommend revision, the article is sent back to the author(s) with the recommendations for revision by the peer-reviewers. After revisions are made, the article is resubmitted and reevaluated.
If the peer-reviewers recommend rejection, the journal does not publish the article.
Single-Blind
Reviewers know the author(s)' identity, but the author doesn't know the reviewer's identity. Most common in the physical sciences and medicine.
Double-Blind
Reviewers' and author(s)' identites are kept secret from each other. Most common in the social sciences and humanities.
Open
Open peer-review refers to the possible modifications of the traditional (single- or double-blind) peer-review process.
Open identities: Authors and reviewers are aware of each other's identity.
Open reports: Review reports are published alongside the relevant article. In traditional peer-review, these are kept confidential.
Open participation: The wider scholarly community is able to contribute to the review process.
Single-Blind
Pros:
The anonymity of the reviewer allows them to be honest without fear of an author's criticism.
Knowledge of the author's identity allows the reviewer to use knowledge of the author's previous research.
Cons:
An author's reputation may overshadow the quality of the work.
Potential discrimination, conscious or unconscious, by the reviewer based on gender, race, or nationality.
Double-Blind
Pros:
The author and reviewer benefit from anonymity and a reduction of bias.
Cons:
Anonymity isn't guaranteed; the author could have a distinctive area of research or writing style.
Knowledge of the author's identity may help the reviewer come to a more informed judgement.
Open
Pros:
Transparency encourages accountability and civility.
Reviewers may be motivated to do a thorough job.
Cons:
Reviewers may be more reluctant to write negative reviews.
Reviewers may be reluctant to criticise the work of prominent researchers, especially in a small research community.