This question already has an answer here:
I need to explain why this sentence is correct. My explanation didn't seem to satisfy the student. The correct sentence is
I've never eaten this before. Do you know what is in it?
Specifically, it is the "do you know what is in it?" part that is confusing the student. Leave out the 'Do you know..' and it is a straight question, ie "What is in it?" Can anyone grammatically explain why the sentence is correct when we add the "do you know.."?