Previously, we learned to use 'what' to ask questions about things.
- What smells?
- The rotten egg smells. ('Rotten egg' = the thing)
To ask questions about people, we use 'who'.
- Who smells?
- Jim smells. He just exercised. ('Jim' = the person)
To ask for the person who does an action, use this structure: Who + [action verb]?.
- Who cooks?
- Who teaches?
- Who owns this cat?
To ask for the identity of a person, use this structure: Who + ['be'] + [subject]?
- Who is the cook?
- Who is the teacher?
- Who is the owner of this cat?