Question words are interrogative pronouns used to ask questions in English.
What, most commonly, is used for questions about general things:
What is your favorite day of the week?
When is always going to ask questions about time:
When is your birthday?
Where is used when we are asking a question referring to a location:
Where you are from?
Why is often used to ask reasons for something:
Why is he running?
Who is always used when asking questions about people:
Who is she?
How is used when we want to ask “a way to do something”:
How do you go downtown?
“How are you?” is one of the most basic expressions in English to ask how a person is doing.
“How are you?”
Response:
“I am fine.”
or
“I am so-so.”