“Auditing” is when you take a course by using university resources without officially registering for it. You can show up to lecture and/or discussion as you feel and, assuming you register and then drop or just ask the professor directly, you can access the assignments and other resources on bSpace, Piazza, bCourses, etc. If you are interested in a courses but do not have time to do all the work and stress out about a grade that is not required for your degree, auditing sounds about as good on a resume as taking it Pass/Fail. If you need to take a course eventually, but are concerned about how hard it is, you can audit it one semester on your own terms and then coast through it the next. Remember that you are paying perhaps tens of thousands of dollars to be here, so take advantage of the university as much as possible.