1、do is used to form questions or negative forms in the simple present tense and simple past tense, followed by the base form of the verb.

2、When there are negative adverbs such as never, seldom, hardly, scarcely, little in a sentence, these adverbs can be moved to the beginning of the sentence to emphasize the meaning. In this case, they are placed before do, forming an inverted structure.

3、In negative interrogative sentences, if the contracted form of do not is used, don’t is placed before the subject; if the non-contracted form is used, not should be placed after the subject.

4、When do is used in imperative sentences to give commands, invitations, advice, or instructions, it should be emphasized.

5、Do can also be used as a substitute verb to make the language more concise.