A collection of articles on a particular issue may be seen as a scholarly dialogue without boundaries of time or space. Some kinds of periodicals are more useful for research than others because of their intended audience, editorial policies, and level of scholarship. It is important to distinguish scholarly journals from popular magazines. You can read a variety of viewpoints in a short amount of time. And sometimes, you may be exposed to ideas or views that never find their way into books.
Articles can be fresh, contemporaneous with events.
Electronic journals, now proliferating on the Web, appear faster than their print counterparts. Originality of ideas or research is a standard requirement of most editorial boards. It has quality control. If you are looking at a periodical with no references, footnotes, endnotes, or bibliography, it's probably not a scholarly journal. Popular magazines vary widely in quality.