Fosse/Verdon assumes its viewers know quite a bit about Verdon, Fosse, and their staggering impact on modern musical theater as we know it. But what about those of us who didn’t audition for high school musicals or wait in line for Broadway lottery tickets on a regular basis? How are we to proceed? Fear not: We’ll get you acquainted with Fosse and Verdon’s legacies. You already know more than you think.