What's the difference between "subtopic" and "subtitle" (when" subtitle" has the same meaning)
can you give a example to explain it ? Thanks!

Question

Answer

A subtitle is just a title, a subtopic refers to the entire text.

The Chimes <= book or story title
A Goblin Story <= book or story subtitle

Dogs <= title of main topic
Dogs are wonderful. There are many different breeds: <= main topic
-- Retrievers are great companions, they come in many colors. <= subtopic 1
-- Poodles don't have fur, so they're very clean. <= subtopic 2