Before you use an article (or any other resource) in your research, you should evaluate the article's quality and appropriateness for your assignment.
Peer-reviewed articles (also known as "refereed articles") have gone through the peer review process prior to publication.
The author's expert peers evaluate the quality of the article and the article's research. 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.
The same journal can publish different types of articles. These article types might not all go through peer review (be refereed).
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.