“When” questions are a type of grammatical construction in the English language that are used to ask about the time when something happened or will happen. They are formed by using the adverb “when” and adding the subject of the sentence and the main verb. For example: “When did you wake up?”, “When will the store open?”, “When is your birthday?”. These questions are asking about the time when something happened or will happen. They can also be used to ask about the frequency of something, for example “When do you usually have lunch?” or “When does the train arrive?”.