What is a sub-topic?

A subtopic

Evey sentence in your paragraph should support your topic sentence. In your topic sentence, you have a controllling idea. For example, you may written this topic sentence:

My three favorite things to do with friends are going to the movie, going dancing, and going out to eat

To support this topic sentence, you must explain to your reader Why these are your favorite things to do with friends. You do ths by explaining how each activity is fun and giving examples to help illustrate your point. All of this is your support.