Peer Review is a term covering a set of practices that collect and apply the judgment of expert reviewers (Identified as expert, not just knowledgeable- so the designation is a political justification as well as a substantive one) to decisions about which manuscripts to publish, which proposals to find, and which programs to sustain or trim.
Understanding peer review requires reflection on both its purposes and values. Peer review circulates research ideas in their formative stages to key gatekeepers in a field. Sometimes this signals others to avoid duplication of effort. Other times it calls attention to a problem that is promising, attracting other researchers and setting off a race for priority (for example, work on cancer genes). Thus, by the time new research is finally published, aspects of its findings and methods may be generally familiar to many in the field, speeding its acceptance and utilization while drawing constructive criticism.
Chubin, D.E., & Hackett, E. J. (2015). Peer Review. In J.B. Holbrook (Ed.)., Ethics, Science, Technology, and Engineering (2nd ed., Vol. 3, oo. 350-354). Farmington Hills, MI: MacMillian Reference USA.