The process of peer review starts with an author submitting and article or a journal. A journal editor then screens and decides whether to reject or accept it. If it is accepted it then gets reviewed by a reviewer. A reviewer is someone based on merit that usually has field or lab work related to the topic. Generally 3-4 reviewers per manuscript. There the editor can asses the reviews and the author can make the decisions to reject or accept the revisions.
The cons of this is that people sometimes take a long time to give back information and there can be a long back and forth before the article is published. This is also a pro though because if there is a lot of back and forth then there is a greater probability that the article is accurate. One con that could impact the credibility of the article is the fact that a lot of scientific articles are about new research or discovery. It would be hard to find someone with the credentials to review if the work is new or not a lot of people have studied it.
