Wh question words are used to ask specific types of questions. There are 6 main wh question words - what, where, when, why, who, and which. Each expresses a different type of information like object, place, time, reason, person, or choice. How is also used as a question word but is technically an adverb. What and how can also function as pronouns, adjectives, or exclamations depending on context. Wh question words are an essential part of asking targeted questions to obtain specific details.