The predicate of the topic sentence, which indicates what will be said about the topic, is called the

Supporting details are what complements an idea. 

Ideas are the key elements of the story and the details that support them. Idea is among the six traits that are very necessary to follow for effective writing. The ideas of the story contains the main message  and the concept of the story. It is also made up of all the other supporting details that develop the theme of the story. A good writer prefers details that are very interesting and informative and not the obvious ones. The writer must repeat what the reader already knows. It is always an edge to be able to convey an idea in the most unique and extraordinary way.