It might be covered in one of the resources, but when people talk about NFTs, they just mean some token on Ethereum that the issuer of said coin say is "the" product. For instance, the NFT for "the first tweet" that sold is just someone created an Ethereum token and said "this one is the first tweet", presumably w/ some text in the token that states the tweet.

In that regard, its kind of centralized. There can be multiple NFTs that claim to be tweets. There's no naturally definitive "twitter" token, unless it's managed by Twitter itself. But you're relying on the issuer of the coin to say "I am the NFT coin" and everyone to agree.

Real world NFTs (e.g. art and collectibles) are unique in that there is no dispute about what the original is. The art was created by the artist or its a forgery. In that regard NFTs rely on some issuing entity that bestows upon itself an arbitrary form of ownership. I can make my own Twitter token and if I get someone to buy a coin for an absurd amount (insider dealing?), and convince reports to write about it, I can be "the twitter nft"

Or am I thinking of this incorrectly?