The process of peer review starts with someone doing research and writing a paper about what they have done/found. They then submit that paper to a publication (typically a journal) that publishes papers pertaining to the topic they have done their work on. The following process varies from publication to publication, but generally, the submitted paper then goes to an editor. If the editor decides that the paper presents good enough science or is pertinent to the publication or if it’s just generally good enough to be published, the editor will pass it on to other reviewers. (The editor could also just outright reject the paper.) The reviewers (funnily enough) will review the paper and write feedback on it. The editor then takes the feedback from the reviewers and passes it and any feedback they themselves might have back to the author. The author then edits their paper based on the feedback they received and resubmit it. If the editor and the reviewers are satisfied, the paper can then be published in the publication.

A definite pro of this system is that it’s a little bit harder to get bogus science into a respected publication because it has to be screened before it can be published. It also means that papers will probably be a little better written/explained. A con is that the reviewers could potentially have their own biases about the subject or the author or any variety of factors. It’s an extremely subjective process, and considering its whole focus is good science, subjectivity isn’t ideal.