what is the difference between questioning with is or do?

Questioning with, "is" and "do" both are absolutely different. If we ask questions using "is" then it can be in simple present tense as well as in present continuous tense. For understanding this term, we'll have to see their structures well. If there is no main verb in the given sentence and if it starts with "is" as a helping verb of this sentence then this sentence will be in simple present tense. For ex:- Is she a good teacher? Is that man really poor? But if there is a main verb in the given sentence and if it starts with "is" as a helping verb then we write the given main verb in its ing - form and this sentence will be in present continuous tense. Ex:- Is he teaching in this school? Is Sita doing this work carefully? Asking questions using "do", is always the sentence of simple present tense when there is a main verb in the given sentence and we use its s/es - form or the base form. Ex:- Do they really like this app?