This assignment requires peer-reviewed journal articles based on original research. Let's break that down:
Peer-review = an editorial practice where an article is sent to other experts in the field for comments before a journal decides to publish that article or not. The reviewers may suggest that the journal accept the article, reject the article, or ask for the authors to make revisions.
Journal = a type of publication where scholars write articles for an audience of other scholars.
Original research= a study that the authors have done
Keep in mind the following considerations when looking for sources to use in your literature review:
For example, if you were looking for an article on apps for mindfulness training, you might find an article that completely focuses on the use of apps for mindfulness training as well as one that only has a sentence or two about apps for mindfulness training. The second one would probably not be very useful to your literature review.
It definitely should! There should at least a few scholarly sources, eg. other academic journal articles or academic books.
Does the author have the education and experience to discuss this subject?
All studies are not created equal. If you are using a source with original research, evaluate the strength of its methodology.