This very good video from CSUCB's Pfau Library will help explain the difference between scholarly and popular articles and how to tell which you are looking at.
You may be familiar with the distinction between primary and secondary sources in the humanities. There, a primary source is an account from someone who experienced the event - a first-person account. A secondary source is written by someone who was not there.
Likewise, a science primary source is written by someone who experienced the event first hand. Just, in this case, the event was the experiment or the gathering of data. A secondary source is written by someone who has read about the research, usually from the primary source.
So how can you tell if an article is primary or secondary?
Other things to look for include:
There are good reasons to use either primary or secondary sources. Secondary sources can catch you up on most of the important research in a specific field, as well as providing over-arching themes and trends in the research. Primary sources give you much more detail on the research, including raw data. A single source may illuminate differences or problems with trends in the larger research body.
In the end you will need to consider both your level of knowledge and background in a field, as well as the specific requirements of your assignment. You may find yourself reading both types of sources to get a deep, comprehensive understanding of your topic.
What is Peer Review?
Peer review, also called refereeing, is a prepublication process used by most scholarly journals. Before an article is accepted for publication, the editors will send the manuscript to outside experts for review. The reviewers will then provide feedback on the quality of the research in the paper. The author can usually make revisions and resubmit the work for final acceptance.
Why do I care if an article is peer-reviewed?
Peer-reviewed articles are the gold standard for academic research. For students, it means that other experts have read and approved the methods and conclusions of the work, providing extra authority to the piece.
How do I find peer-reviewed articles?
Use subject databases that specialize in the field, which are more likely to include peer-reviewed journals. Many databases also include a "peer-reviewed articles only" checkbox.
Where can I learn more?
Get a quick introduction to peer review, find advanced materials, even learn about what happens when peer review doesn't happen at Scrutinizing Science from Understanding Science: How Science Really Works.
Need to be absolutely certain that an article has been peer-reviewed? Use UlrichsWeb! This database provides a range of information about a journal from publisher to title history. Peer-reviewed journals are indicated by a symbol that resembles a sports referee's jersey on them.
**Tip: Remember to search by the name of the journal, not the title of the journal article.**