Law journals and law reviews are regularly-published issues containing articles written by practitioners, professors, and even students about various legal topics. These articles are in-depth explorations of the author's chosen topic in an academic article format. They contain extensive citations to a variety of different primary and secondary sources. Different journals will have different coverage of legal topics; they may be general interest publications or cover a specific type of law.
Other types of more formal publications include state or national bar association magazines, trade publications, and other legal organization publications. These types of publications will generally be shorter and not as thorough as traditional law journal articles. They are aimed at practitioners and often deal with current topics.
Journal articles are a great way to find citations to sources that are relevant to your legal issue. Because journal articles are comprehensive studies of a problem in the law that undergo an editing process, you can cite to them for their ideas when citations to publications are appropriate. However, journal articles are not the law. They will often propose solutions to legal issues or discuss potential outcomes to novel legal controversies, but they are at best a persuasive source. Be sure to go to the cited case law/primary authority for sources you can rely on.
Additionally, although journal articles undergo an editing process, often by student editors on a law school journal, journal articles are not updated in the way that encyclopedias and other secondary sources are. ALWAYS check that the source material referred to in the journal, as well as the overarching article premise, is still good law or has not been negatively treated. Journal articles are a great way to find creative legal arguments and propositions, but you need to do your due diligence to ensure that those same ideas are still worth citing.
Journal articles are available on Westlaw, Lexis, HeinOnline, the TTU Law Library catalog, and Bloomberg. Additionally, you may be able to find them through Google/Google Scholar and the website of the journal that published the article.