pathology is like, addison's disease is adrenal insufficiency. you get hyperpigmentation, yadda yadda yadda.
pathophysiology is like, WHY do you get hyperpigmentation? because ACTH is related to POMC (proopiomelanocortin) which leads to hyperpigmentation.
so path is just, this disease is this that and the other.
pathophys is, why does this happen? (much harder in my opinion).