Academic journals contain articles that have a more specific focus on one aspect of a topic about literature. Articles contain the most up-to-date research and those found in scholarly journals are most likely peer-reviewed, meaning they have gone through a formal review and editing process by experts in the discipline. Articles in magazines, newspapers, or other "non-peer-reviewed" publications do not undergo this process--they are accepted at the discretion of a single editor.
In general, the most valuable and thoroughly researched information on literary topics can be found in scholarly, peer-reviewed journals, and these sources are what you should look for and use for papers in the English Department. For more detailed definitions of terms used here, check the page in this guide called Library (and Literary) Terms and What They Mean.