Question
Word

Function

Example

what

asking for information about something asking for repetition or confirmation

What is your name?
What? I can't hear you.
You did what?

what...for

asking for a reason, asking why

What did you do that for?

when

asking about time

When did he leave?

where

asking in or at what place or position

Where do they live?

which

asking about choice

Which colour do you want?

who

asking what or which person or people (subject)

Who opened the door?

whom

asking what or which person or people (object)

Whom did you see?

whose

asking about ownership

Whose are these keys? Whose turn is it?

why

asking for reason, asking what...for

Why do you say that?

why don't

making a suggestion

Why don't I help you?

how

asking about manner

How does this work?

asking about condition or quality

How was your exam?

how + adj/adv

asking about extent or degree

see examples below

how far

distance

How far is Pattaya

from Bangkok?

how long

length (time or space)

How long will it take?

how many

quantity (countable)

How many cars are there?

how much

quantity (uncountable)

How much money do you have?

how old

age

How old are you?

how come (informal)

asking for reason, asking why

How come I can't see her?