A peer reviewed journal or article is one in which a group of scholarly reviewers in the subject area of the journal reviews the content for quality of research and adherence to editorial standards of the journal. If you use materials from peer-reviewed publications they have been vetted by scholars in your field for quality and importance.
You can limit your search results to peer reviewed materials in many library databases.

Literature across all fields of science and social science. Comprehensive coverage of literature across all fields of science and social science. Provides access to more than 850 of Elsevier's primary research journals, which focus on scientific, medical, biomedical and technical areas.