Peer review is to add credibility to research. It gives the opportunity of other scientists to review the research and fact check so that when it is reviewed by other people, they have more confidence in its accuracy and the fact that many people have looked through the material with a fine toothed comb.
A con of peer review is if the reviewer is not an expert or inept in that particular field, so their feedback could be inaccurate or out of context.
