I tried to explain supervision trees.
My best try is:
ok, You get a chocolate box from the factory, with warranty, "Every bit will taste good." Then if you find that one bit taste funny. You can throw the whole box away. Because you get a new from the factory. That is like supervision trees in Erlang. If one thread misbehave. There is a risk that all threads have bad state. If that is the case, the supervisor throw all threads away and start over. Like the chocolate box, you are the supervisor when you throw the box.