A paper is normally peer reviewed before it’s published to assess its quality and to “certify” it by a panel of experts in the field. They might identify errors or weaknesses that could change the interpretation of the results. If they do identify errors, the paper is sent back to the author to redo experiments or make the requested changes before being resubmitted for review. Once the reviewers accept the revisions, the paper can be published.
Because this process can take a long time, some researchers present abstracts at conferences without peer review, or submit manuscripts to MedRxiv. MedRxiv is a preprint server that accepts manuscripts that have yet to be peer reviewed, in order for other scientists to discuss the findings.
Research from sources that are not peer reviewed may not be accurate.