Course levels are prefixed by the year: 1 or 1x or 1xx for first years, or introductory courses; 2 or 2x or 2xx for second year, and so forth. The term 'psychology 101' is sometimes used jokingly to say that a certain stated opinion is either very obvious or basic, or that it is immature and ill-considered. 'Philosophy 101' and so forth are similarly used. Or they could, of course, be referring to can actual course!