"Yes, I do!" turns out to be the most popular words for people in love all around the world, most of whom do not know a word of English language.
I think the original question for this emotional confirmative answer should have been "Will you marry me?" But grammatically, it is not the case, right? Is it "Do you love me?" or "Will you marry me, do you think?" or "Will you marry me, do me a favour"?
Best Answer
"Yes, I do!" answers a Do-question. One of those you already mentioned, "Do you love me?" Other questions would include "Do you want to be with me?" and "Do you have feelings for me?"
To the question "Will you marry me?" the answer would be "Yes, I will."
To a question like "Are you going to marry me?" the answer would be "Yes, I am."