Ulrich's Periodicals Directory (often referred to as UlrichsWeb) is a database that the University Library subscribes to. You may be told to "check Ulrich's," but what does that mean?
Ulrich's will tell you if a journal is still in print, available online, where it is indexed, and most critically, what type of journal it is (scholarly, trade, popular, etc.). This is useful not only for students being asked to find specific types of sources, but also for faculty considering where to publish regardless of where they are in the RTP process.
Ulrich's does not tell you if a journal is good or bad. It just gives you classifications and you make the final judgment.
Finally, you can send information/updates to Ulrich's.