We use when to ask for information about time.
For example:
When do we have class?
When are you going on holiday?
When do you finish your career?
We use why to ask for information about a reason.
For example:
Why are you sad?
Why are you studying English?
Why do you like to go to the beach?
We use how to ask for information about a way or quality/quantity.
For example:
How old are you?
How are you?
How many brothers do you have?
We use what to ask for information about things, ideas and actions.
For example:
What is your name?
What are you doing?
What kind of music is your favorite?
We use who to ask for information about a person or people.
For example:
Who wants an ice cream?
Who is your friend?
Who is running in the park?
We use where to ask for information about a specific place.
For example:
Where are you from?
Where were you born?
Where do you live?