A topic sentence is the first sentence in a paragraph.
Gives you a idea of what the paragraph will be about like a introduction.
A concrete detail is like the meat of a burger like the the words in a page.
Without the details the topic sentence is nothing and saying that paragraphs are good would be just bluffing.
A commentary is the extra in a paragraph.
gives your sentences more details and gives them more meaning.
A concluding sentence wraps up a everything.
Its the finishing touch of your paragraph.
Without a concluding sentence your paragraph wouldn't seem like its finished.