Wh-questions
When do we use "who" in a question?
When we refer to people.
When do we use "what" in a question?
When we refer to things.
When do we use "where" in a question?
When we refer to places.
When do we use "when" in a question?
When we refer to time.
When do we use "why" in a question?
when we refer to a reason.