Periodicals are usually categorized as either popular, trade, or scholarly. The main purpose of periodicals in this category is to provide information, in a general manner, to a broad audience of concerned citizens.
Scholarly periodicals report on original research, theory, or experimentation.
Scholarly articles are written by experts in their subject, who meticulously cite related research in the form of footnotes or endnotes. The language used in scholarly journals is that of the discipline covered. For the most part, universities are more interested in the scholarly publications than the popular or trade, and collect primarily in that category. Each periodical issue contains a wide variety of stories or articles, usually quite unrelated to one another. These are still very useful, especially if you need information from articles printed before 1980.