When is the pronoun what used in a sentence?

The pronoun 'what' is an interrogative pronoun (introduces a question) and a relative pronoun (introduces a relative clause); for example:

Question: What is your name?

Relative clause: You can do what you want.

The Word 'what' is also and adjective: What movie did you see?

The Word 'what' is an interjection: What! That's a lot of money.