The concept for the class is basically learning how to incorporate design basics into scrapbooking design. Each week focused on a different design concept, like balance, repetition, unity, etc, which Cathy explained in a slideshow/video (which were usually like 40+ minutes long, lol!) and then showed examples of it in her own work. There were also sketches (usually at least 3) for each week, in Cathy's simple, clean style, designed to give you practice using that week's concept. Last year she only included sketches but someone in the class made templates each week for digi-scrappers to download. Looks like Cathy will be including them herself this year.
If you're looking to learn a big more about design, then I would definitely recommend taking it. I had taken some design classes in college so I had an understanding already of the basics but even so I still learned some things I didn't know, and I have noticed myself thinking about them more when I do my own layouts, which was kind of the point, haha. But yeah, it was a lot of fun! Highly recommended!