ruby on rails - What is the difference between active record callback and association callback? -

I know how callback works and when calls are received, such as active life of the recorded callback In Hook Active Records Objects, which allows you to work with those objects at different points.

But I am not clear how association callback calls, I found in Ruby on Rail Guide, that the association callback originated from events in the life cycle of a collection. When I get a call at that point, I am not clear.

I would be happy if someone gave me some examples and explained here.