Peer review is part of the procedure for working out if research in physical Science or social science is valid and has been round for over 300 years. Usually but not always peer review works.
Basically peer review involves getting experts working in the same field and hopefully independent to review new work and agree or disagree with the result. A larger, disinterested group of scientists is more likely to notice flaws in scientific work than those who did the actual work, hopefully cronyism should be prevented. Peer reviewers decide if work is good, also if it’s original, they may recommend improvements to research.
Whether science gets published in a good, peer reviewed journal depends on successful peer review.
Getting work reviewed and repeating experiments is an important part of the Scientific method.
Some critics believe that peer review has a built-in bias against highly original works and results because reviewers (as do people in general) tend to be more tolerant of works and results that are consistent with their own views and more critical of those that contradict them. It should be kept in mind that history is replete with examples of innovations that were originally ridiculed by their peers because they contradicted the common wisdom of the day2. The bias by academics against highly innovative work may be in part a result of the fact that they have vested interests in maintaining the status quo after having spent many years or decades supporting it. 
Peer review and the InternetEdit
Because it allows anyone to publish and to do so at virtually no cost, the Internet makes it much easier to give swift and widespread exposure to highly innovative and controversial works that might have a difficult time being getting into mainstream, peer reviewed hard copy publications. However, there are so many articles and other items of obviously dubious quality on the Internet that it can be difficult to find those that are truly promising. 
- ↑ 1.0 1.1 Peer Review Definition
- ↑ How Scientific Peer Review Works;Peer Review: The Basics
- ↑ Peer Review Definition