This is the 1984th most frequent Korean word.
무엇인지
"무엇인지" means "what it is" or "whether it is what."
Here, '무엇인지' is used to refer to an unidentified object or concept, functioning as the subject of the curiosity.
사람들이 무엇인지 몰라서 궁금해했어요.
People were curious because they didn't know what it was.
In this sentence, '무엇인지' serves as an indirect question within the attempt to find out its identity.
그것이 무엇인지 알아내려고 합니다.
I am trying to figure out what it is.
This usage of '무엇인지' forms part of the direct question regarding an unknown item or concept.