Scholarly journals are an important part of faculty research, as well as RTP (retention, tenure, promotion).
Here are some qualities that set them apart from "popular" sources such as newspapers, magazines, etc.
The purpose is to communicate research and scholarly ideas.
Authors are researchers, scholars, and/or faculty, and they will typically have an institutional affiliation listed.
The audience is other researchers, scholars, and/or faculty.
The coverage tends to be focused and narrow, with the exception of a publication like Science, which is quite broad.
Publishers are usually university presses, professional associations, academic institutions, and commercial publishers.
Articles in scholarly journals should have a works cited/references/bibliography with full citations.
Articles in scholarly journals should be peer-reviewed/refereed. Elsevier has a thorough description of peer review, including how it works for authors. Remember that the "peers" in peer review are other scholars, researchers, and faculty. Also, peer review can take months if not years--from the time that an article is submitted to its review and ultimate publication can easily take 12-18 months.
Examples of scholarly journals include Journal of Politics, Sociological Review, and Journal of Marriage and Family.
Note that some parts of scholarly journals are not peer-reviewed: these include book reviews and letters/responses to the editor.
The other "big" type of publication is a trade journal. Most trades are not available at a newsstand, rather they are either published by a professional organization, union, or business. Examples of trade journals are Hollywood Reporter, Columbia Journalism Review, and Chemical Bulletin.
The purpose is to inform and educate a specific audience of people within a certain trade--and unlike scholarly journals, trades may be published monthly or even weekly versus quarterly.
The coverage, similar to scholarly journals, is quite focused and not intended for a general audience.
Articles may have a few citations or references, but not as many as a scholarly publication.
Authors are members of a field or profession, versus journalists, and may be compensated for writing a column or article.
Popular sources can also play a role in faculty scholarship. Sometimes a short article in a newspaper or magazine can refer to an academic study, piquing the interest of other academics.
The attributes of popular sources are quite different from scholarly ones.
The purpose is to inform and entertain the general reader.
Authors tend to be journalists or professional writers (and they are paid, unlike authors of scholarly articles).
The coverage is much more broad, again catering to a more general audience.
Publishers are almost always commercial: Dow Jones, Hearst, etc.
Popular sources tend not to include citations or references, and will also contain ads.
Popular sources are published more frequently (it is the peer review process that can slow academic publishing).
Examples of popular sources are the Wall Street Journal, Vogue, Psychology Today, and The New Yorker.
More on Peer Review
One way to serve your profession/field of study is to serve as a peer reviewer. It is also helpful to know what reviewers are looking for, so when you are interested in identifying a journal and submitting an article, you are better prepared. Typically, when an editor is seeking a reviewer, he or she will make a call on the journal's homepage, or through a professional listserv.
Here is an example of a call for reviewers from Oxford University Press' Lab Medicine.
There is another benefit of serving as a reviewer. If you assign your students to use a peer-reviewed article as a source, you can explain the process having seen both sides (reviewer and author).