What Is the Peer Review Process?

Please can you explain how the peer review process works? Does the fact that a clinical study has appeared in respected peer review journal mean that it has effectively passed peer review? Or can anyone publish their trials and it is upon publication that the true scrutiny really begins?

If the latter, when are the trials officially deemed to have passed peer review, given that the experts may well have differing opinions on their robustness and on whether there are any protocol errors?

A good overview of peer review can be found at Wikipedia.

Peer review is done when an article is submitted for publication in a journal that has editors capable of reviewing the technical and clinical details of the submitted material. Differing options are often published along with the article.