A periodical is often the best source for information on new or current topics. The subject may be too narrow for publication in a book.
Old periodicals contain historical information.
If the journal reports on original research or experimentation, it is considered a scholarly publication. If the journal's primary focus is to entertain, to sell a product, or to promote a po int of view, it is considered non-scholarly. If the answer is yes, may be a scholarly journal since they always cite their sources. Scholarly publications usually have a serious appearance, often supplemented by graphs and charts. Scholarly publications are written by scholars or researchers in the field.