How can you tell? The chart below outlines differences among various types of publications.
The Libraries at North Carolina State University do an excellent job of explaining the structure of an empirical research article in this video:
Peer review is the process by which the quality of an article is evaluated by other authors or scientists in the same field (aka "peers") before the article is published.
This 3-minute video illustrates the process of peer review.
Most library databases identify articles as peer-reviewed or allow you to filter your results to peer-reviewed articles.
If you are unable to limit your search to peer reviewed, or cannot tell whether an article you have found is from a refereed journal (one that uses a peer review process), search for the journal title in the Ulrichsweb database or Ask a Librarian: