I have a problem with such sentences:
I'm not sure about what is there.
I'm not sure about what there is.
I know that both are correct and that their meanings are different, but I don't see the difference.
For example, there are three people and one of them says "The book is on the shelf."
One of the two who were listening asks the second. "What is on the shelf?"
The second answers "I didn't hear that, I'm not sure what there is/is there."
Please, help me, somehow.
Thank you in advance.