Peer-review is a process that begins when an author submits their paper to a journal. In the peer-review process, a group of researchers/scholars, who are experts in the subject area, review the paper before it is permitted to be published as an article in a journal. This process is often called a "blind review" because the peer-reviewers do not know the name of the author.
Peer-reviewers are also called referees. They evaluate the manuscript for quality and significance. Peer-reviewers will make suggestions to the editor of the journal on ways to improve the manuscript. Sometimes, peer-reviewers will recommend that the article not be published because the quality of the research is poor.