Peer review means that the articles that appear in this type of journal have been checked by other experts in the field. These experts will then tell the publisher that they are suitable for publication in their journal. Material that appears in peer-reviewed scholarly journals covers all subject fields and may include original research, criticism and reviews of research.
You can safely use this type of material in your work as you know it has been through a review process before it has been published. Peer-reviewed material can be found on the Internet. Just be careful and check any information before you use it.