The emphatic forms of a verb are often used to give greater emphasis to the idea express by the verb. The auxiliaries do, does and did are used to give this additional emphasis. The emphatic forms are used in only two tenses, the present tense and the past tense.

When do, does, and did are used in questions, the form is not for emphasis. The use of do, does, and did in questions is an idiomatic way of asking questions in English. In the following questions do, does, and did are not the emphatic form of the verb.

  Do you have to go now?
  Does he want to eat tonight?
  Did she buy that hat this week?

Also when do, does, and did are used to mean accomplish, carry out, etc., the form is not used for emphasis in these cases. Here are examples of that:

  I do my homework after class.
  He does a good job every day.
  We did our best work today.