Peer review is science’s own method of quality assurance. It refers to a process in which a journal, conference, or book publisher requests experts in the field to conduct a preliminary evaluation of the manuscript intended for publication.
The process involves assessing aspects such as the comprehensiveness of the data, mastery of the theoretical framework, and the reliability and accuracy of the research implementation. This process helps identify potential errors and improve the quality of the research.
The reviewers of the publication are independent in relation to the manuscript being evaluated. The review can be conducted either anonymously or openly. 
Image source: https://wiki.eduuni.fi/spaces/csckjmo/pages/338179483/Peer+review
The JUFO Portal is a service you can use to check whether a journal is scientific (peer-reviewed) or whether a book publisher is reliable.
The Publication Forum (JUFO) is a Finnish classification system that evaluates the quality of scientific publishing. The classification includes journals, book series, conferences, and book publishers. The evaluation is carried out by discipline-specific expert panels, which categorize key domestic and international publication channels into quality levels:
3 = highest level
2 = leading level
1 = basic level
0 = do not (yet) meet the criteria for level
Not evaluated = has not yet been evaluated or is professional or non-academic.
You can search the Publication Forum database without logging in.
Although the number of evaluated publications is large, the JUFO Portal does not include all journals and book publishers in the world.
In the JUFO Portal, type the journal's name into the Free text search box. If the journal is classified at level 1, 2, or 3, it is peer-reviewed.
Level 0 includes a variety of publication channels with differing levels of quality and purpose. These may include professional magazines, questionable open access journals, university publication series, and journals that have not yet been classified.
Please note that the Publication Forum classification does not cover all scientific journals worldwide. Therefore, if a journal is not listed or is placed at level 0, it does not necessarily mean the journal is of poor quality.
If the journal is not found in the JUFO portal, try the following alternatives:
A book publisher does not need to publish only scientific books to be included in the Publication Forum (JUFO) classification. Therefore, additional criteria are needed when evaluating the quality of a book.
In the JUFO portal, enter the publisher’s name in the Free text search field. If the publisher is classified at level 1, 2, or 3, it is considered reliable.
In addition to peer review, it is useful to pay attention to the number of citations an article has received. This refers to how many times the article has been mentioned in the reference lists of other articles within the same database. The number of citations helps assess the article’s impact and importance within the scientific community.
Citation counts can also be used to evaluate journals, researchers, universities, and the research output of different countries. A high number of citations may indicate that the article has been valuable to other researchers.
Read more: Responsible use of publication metrics at the University of Oulu
