Neither of you are correct, technically, although you shouldn't feel bad about that as it's what 99.9% of people think. An NFT is a representation of ownership on the block chain ledger. It can represent ANYTHING, houses have been sold as NFTs as well as many other things.
I'm curious about the claims of the guy above you as well, I certainly don't know for sure, but I don't see why it should take incredible amounts of energy to maintain block chain, and it sounds like that user is conflating crypto mining with NFTs.
Note: I am not promoting either, please don't buy crypto or pointless NFT images!