Depending on the field, assignment and professor, you may be asked to find peer-reviewed or scholarly articles.
Peer Reviewed: Peer-reviewed articles are predominantly found in the science and medical disciplines. The articles are reviewed by multiple experts (peers) in a highly structured and critical process. The author then receives that feedback, makes changes and resubmits the work, and then the journal editor decides whether to publish it.
Scholarly: These articles are research focused and written for an academic audience; they most likely have only been reviewed by an editorial board, rather than content experts.