You're letting someone know that you are not sure about what is being asked. You may also have no knowledge or opinion on a topic. Examples: "I don't know what to eat for dinner." "I don't know what to buy you for your birthday." "I don't know what to say." "I don't know what to do with my spare time." "I don't know what to do for vacation." "I do not know what to do to make you happy." "I do not know what to do to help you understand." "I do not know what to think." "I do not know what to do to prevent this." "I do not know what to order."
You are asking someone in present tense if they object to something you are asking. Examples: "Do you mind if I excuse myself?" "Do you mind if we left early?" "Do you mind if I take a nap?" "Do you mind if I ask your mom?" "Do you mind if it snows?" You could also use the word 'would' Examples: "Would you mind if we went out to eat?" "Would you mind if I opened the window?" "Would you mind telling me what you're doing?" "Would you mind being quiet for a minute?" "Would you mind if I changed the channel?"