Causative form is used to show that one is forcing or allowing another to do something...passive causative form is just the passive form of that, putting the emphasis on the person being acted upon rather than the person doing the acting. Causative passive is used pretty rarely, and many times you'll find a truncated version (~される instead of ~させられる). Many times you will also find that the person forcing/allowing the action is assumed rather than states.
そんな事お前にさせない! - I won't let you do such a thing!
メニューを見させていただけないでしょうか? - Could you let me see the menu, please?
いやな事を[誰かに]させられた! - You were being made to do things you didn't want to.
許されるなら - If it is allowed (FMA Opening)
Hopefully this will help you more than confuse you. I'm sure there are others on this board better at explaining this distinction than I am.