Answer:
A theme is like a statement about the message the writing was trying to get across, while a main point is more like a topic.
Explanation:
A theme will almost be a moral, and it is generally expressed in a sentence. A main idea is like a general thing that applies to the writing. You can build a theme statement off of a topic.
For example:
Topic/Main Idea: Friendship
Theme: Friendship is a powerful force
(Ik that is cheesy but its the best example I could come up with lol)
