As we seen from the previous post, there was :

이것은/ 그것은 / 저것은 ] 무엇입니까?

The 무엇 is treated as a noun

There are several question words that are used to be used, such as :

No Question word Meaning
1. 무엇 what
2 누구 who
3 온제 when
4 어디 where
5 얼마 how much
6 왜 why
7 어떻게 how

all of these words can replace 무엇 and treated as a noun.