The evaluation and approval process of a research paper by acknowledged experts in the same field, prior to publication of the paper in a scientific journal.
Peer reviews check the originality, quality, and validity of the research by asking questions that the authors need to answer satisfactorily before the paper is approved for publishing. This essential process increases the chances that the information that goes out to the public can be trusted. However, even the most highly regarded journals can make mistakes as witnessed during the COVID-19 pandemic with a paper on hydroxychloroquine which was published and then had to be retracted.
Examples of leading peer-reviewed journals are The Lancet, the British Medical Journal, New England Journal of Medicine, and Nature – all of which publish extensively on COVID-19.