If you want to know the time of the party, what question word should you use?
When
If you want to know the reason for the party celebration, what question word should you use?
Why
If you want to know the people invited to the party, what question word should you use?
Who
If you want to know the location or place of the party, what question word should you use?
Where
If you want to know the theme of the party, what question word should you use?
What