Most Philosophy (PHIL) courses are assigned an upper-case letter A or B on the Courses section of the department's website; the letter is put in parentheses at the end of the course description. (Undergraduates should ignore any roman numerals at the ends of course descriptions—those are for the graduate program.) The primary function of the field designation is to enable majors and minors to determine which courses satisfy their distribution requirement. But this system is also helpful in indicating the focus of some of the courses where this may not be readily apparent.
A = Practical Philosophy (ethics, social and political philosophy, aesthetics): Courses in this area focus on such topics as the nature and justification of moral requirements, social justice and political legitimacy, the character of aesthetic judgment, and the nature of representation in art.
B = Theoretical Philosophy (philosophy of science and mathematics, metaphysics, epistemology): Courses in this area focus on the fundamental categories involved in our understanding of the world (causation, substance and change, universals and particulars, and the nature of mind), the character and basis of human knowledge, the criteria and goals of scientific explanation, the relation between theory and evidence, and the nature of mathematical knowledge and proof.
Not sure if a PHIL course you took counts as field A or B? Get in touch with Tyler Zimmer, Assistant to the Director of Undergraduate Studies.