Peer reviewed articles are often considered the most reliable and reputable sources in that field of study. Peer reviewed articles have undergone review (hence the "peer-review") by fellow experts in that field, as well as an editorial review process. The purpose of this is to ensure that, as much as possible, the finished product meets the standards of the field.
These terms are interchangeable with each other, and these articles are not always peer reviewed/refereed. These articles are still research focused and heavily sources (lots of references), and written for an academic audience, but they may have only been reviewed by an editorial board, rather than content experts. This does not necessarily take away from the importance of the publication or its legitimacy as a valid academic source.
Peer reviewed publications are one of the main ways researchers communicate with each other.
Most library databases have features to help you discover articles from scholarly journals. Most articles from scholarly journals have gone through the peer review process. Many scholarly journals will also publish book reviews or start off with an editorial, which are not peer reviewed - so don't be tricked!
Peer reviews are conducted by scientific experts with specialized knowledge on the content of the manuscript, as well as by scientists with a more general knowledge base. Peer reviewers can be anyone who has competence and expertise in the subject areas that the journal covers. Reviewers can range from young and up-and-coming researchers to old masters in the field.
Scientific papers submitted for peer review usually follow a specific structure that begins with the title, followed by the abstract, introduction, methodology, results, discussion, conclusions, and references. The title must be descriptive and include the concept and organism investigated, and potentially the variable manipulated and the systems used in the study.