use of do and have

I hav a problem in the use of DO in the sentences
Do come in
Do send me
wat role do play here.
second where we use :having

Gurvinder kaur

“Do” just emphasizes the strength of the invitation. It doesn’t serve any grammatical purpose.

I also agree with Jamie. It just use to emphamsize. The second question is not clear.Can you describe more understandable?

I don’t understand the second question.

Maybe Gurvinder Kaur is talking about sentences such as we are having a party, we’ll be having a meeting next week, etc?[YSaerTTEW443543]

TOEIC listening, question-response: Do you know when our new computers will arrive?[YSaerTTEW443543]