In general, peer-reviewed articles are publications that have gone through the peer review process and been accepted to a publication based on scholarly merit.
Often, assignments will require that you use only peer reviewed sources in your research for this reason! If you only want your search results to include peer-reviewed results, click the Scholarly (Peer Reviewed) Journals limiter in the database. Here's an example of that limiter within EBSCO databases:
Be aware: some of the results, though contained within a scholarly journal, may not be peer-reviewed if they are book reviews or editor's notes that come with other peer-reviewed publications!
If you have questions about whether or not something is peer-reviewed, or would like help finding peer-reviewed articles, contact us via AskAthena!