'Periodical' is an umbrella term for newspapers, magazines, journals - any title published regularly or irregularly. The Library subscribes to thousands of scholarly journals both in print and (mostly) online. You will come across journal articles many times in the course of your studies; they may appear on your reading list and your lecturers will encourage you to consult journal articles when you're doing research, particularly when preparing your literature review.
Journal articles are excellent sources of scholarly information because they can provide very in-depth, up-to-date coverage of a subject; they are typically very structured and written by experts in a given field. Crucially, like books, journal articles that appear in scholarly academic journals are "peer-reviewed" which means they have been critically reviewed and evaluated by a panel of experts before being okay-ed for publication. All of this means that you (as researchers) are assured of the excellent quality of information in a published journal article.
Before databases came along, we relied on indexes, abstracts, contents pages, and a whole lot of reading when trying to find material relevant to our research.
Databases are incredibly powerful engines that allow us to search the content of thousands of journal articles by keyword, as well as provide us with digital access to the full text of many of them. Some databases are multi-disciplinary whilst others are discipline-specific.
Lots of our databases are made available to us via the nationally funded IReL consortium (IReL stands for the Irish Research eLibrary), some we subscribe to as an institution; others are freely available online.
Click for access, then sign in with your DCU username and password where required.