An access code is a password you use to access course content online. The content you access depends on the course, but can include things such as practice exams questions, interactive videos and course assignments. If your professor requires you to purchase an access code, it is because at least part of your grade will be related to and/or come from the online content. If your professor recommends that you purchase an access code, it is probably because the online content gives you access to additional study material.
