Peer-review is a publication process where research articles written by experts in academic or professional fields are submitted to reviewers who are also experts in the field.
To locate peer-reviewed articles, Summon and most library databases will provide a peer-review limiter that limits results to journals that publish research articles with a peer-review process. Letters, commentaries, news reports, obituaries, book reviews are generally not peer-reviewed, even if the journal uses a peer-review process for research articles.
In rare cases, databases may have an error about a journal's peer-reviewed status. To be absolutely sure if a journal uses a peer review process, use Ulrichsweb.