This is an essential prerequisite for participation in any discussion about materia medica or case histories. Of course, what happens immediately is that students want to know why this classification exists. As tutors we emphasise the importance of the classification by relating it to practice. This immediately involves students in a higher level of homeopathic knowledge. Here the student is discussing not just understanding facts, but evaluating them.
Hierarchy is about attaching relative values to symptoms.
Educators generally consider making judgments about the relative value of different aspects of factual material a high order skill. For those who wish to follow the classification of cognitive skills further, you will find Bloom's Taxonomy referred to in many educational books. This is probably the best place to begin as you are likely to be presented with a discussion of the strengths and weaknesses of Bloom's work. I find his classification helps me to orient myself with a range of difficulty. See the bibliography for Bloom's original work.