什么【shénme】

什么 asks "what", in the slot where the answer belongs.

In front of a noun it means "what kind of"

No measure word, unlike 哪.

什么 against 哪个

什么 asks openly, with no options on the table. 哪个 asks you to pick from a set both speakers can see.

Fixed questions built on 什么

什么时候 asks when, 为什么 asks why, and 叫什么名字 asks a name.

什么 as "anything" and "nothing"

Followed by 都 or 也, it stops asking.