Either type of question is derived from a related statement sentence, and in English we have a certain template for how to turn a statement into a question. Some reflection shows that word order is a large component of asking a question in English.
Identity Question Statement: You want a cat. Question: What do you want? Notice that in the question, the order of "you" and "want" is reversed and the word "do" is introduced. | "Yes/No" Question Statement: Yes, you are eating a grapefruit. Question: Are you eating a grapefruit? Notice again, that reversing two words signals to the hearer that a question is being asked. |
Identity Question Statement: Bạn muốn một mèo. Word for word: You want a cat. Question: Bạn muốn gì? Word for word: You want what? The noun "a cat" was replaced with the word for "what" with no other changes to the sentence. | "Yes/No" Question Statement: Vâng, bạn đang ăn một bưởi. Word for word: Yes, you are eating a grapefruit. Question: Bạn có đang ăn một bưởi không? Word for word: You yes are eating a grapefruit no? The word "có" was added before the verb and the sentence ends with "không." |