Hi Mrs/Mr. <blank>, I should type my essay because it's more efficient, you can finish grading everyone's essay quicker, and turning it in online ensures that plagiarism will be caught if I happen to use any; this benefits us both.
In paragraphs, a stated main idea is called the topic sentence. In an article, the stated main idea is called the thesis statement. When the author does not state the main idea directly, it is called an implied main idea.