As the title suggests, this course is about drawing shadows. It's a slightly technical subject but shading have a huge impact on aesthetical values and an atmosphere of an artwork. It gives an impression of 3-dimentionality and even reality to flat drawings. if it's placed correctly of course.
I've noticed that many shading tutorials explain vaguely this phenomena on examples of apples and other fruits. Well, these classes are focused on geometrical shapes and solids. Don't worry, these lessons are really short and concise.