The Catalogue is laid out exactly like the App Store and iBookstore, so everyone is already familiar with how to browse it and subscribe to courses. The iTunes U library is where you'll find all the courses you are subscribed to and it looks similar to the bookshelf in iBooks.
Inside a course, you'll find all the info an instructor chooses to share about the class, including catalogue information and the course outline, structure, and syllabus. Instructors can also make posts to the course with more information about lectures as well as documents and videos. Additionally, students can take notes in a designated area of the course page and quickly access all course materials.
As a college instructor, I look forward to using iTunes U as a way to supplement content and materials for my classes.