Peer-reviewed articles (also known as "refereed articles") have gone through the peer review process prior to publication.
In the peer review process, the author's expert peers evaluate the quality of the article and the article's research. Very often, the author(s) will have to revise their articles and make changes before resubmitting. The publisher publishes the article only after the article has been approved by the expert reviewers.
If an article is peer-reviewed, you can be more confident in the article's quality.
There are a few different ways to check if an article is peer-reviewed. Each journal may represent the peer-review process differently.
If you search for articles in a database like Academic Search Complete, you might have the option to filter to show only peer-reviewed articles. In Academic Search Complete, this option is in the Advanced Search screen. There is a checkbox to filter to show only peer-reviewed items.
If you use a different database, or no database at all, to find articles, you will have to do the investigating yourself.
Some publisher website layouts will have peer-review process timestamps like this:
Sometimes, only the article's PDF will have these timestamps.
You have searched a database (or Google Scholar) and have found an article about your topic! It has great keywords, and the abstract is interesting. Before you use the article in your research paper, pause and check:
What kind of article did I find?
The same journal can publish different types of articles. These article types might not all go through peer review (be refereed). Not all article types will be appropriate for your research. The type of article should be listed by the journal, but it isn't always. Article types can include book review, editorial, opinion piece, case study, research article...
Not all publishers label their article types! Be on the lookout to check what type of article you have accessed!
Look at different article types with me in this Article Types Video.
Book reviews are written to help people decided if they are interested in reading a book. Book reviews are usually not peer-reviewed. They do not include research. Book reviews are likely never a good resource choice when researching a topic.
Book Review Example. You can identify a book review by its common elements:
Editorials are written by the editors of an entire journal or a specific journal issue. Editorials are usually not peer-reviewed. They do not include research. Editorials are not likely to be a good research choice.
Editorial Example. You can identify an editorial by its common elements:
Opinion pieces are written by anyone. Opinion pieces are usually not peer-reviewed, but they may have been reviewed by an editor before publication. This is not as rigorous as peer-review. Opinion pieces are not likely to be a good research choice, unless you are researching something like a discipline's attitude towards a subject.
Opinion Example. You can identify an opinion piece by its common elements: