In sentences with an interrogative mood, the auxiliary verb will often come before the subject of the sentence. A question mark is also always required for proper punctuation.
(it is essentially any sentence you ask something in. I.e: How is the weather today? Is Jack ill? Etc..)
Interrogative sentences are generally divided between yes–no questions, which ask whether or not something is the case (and invite an answer of the yes/no type), and wh-questions, which specify the information being asked about using a word like which, who, how, etc.
