To be specific, an NFT can be anything - even a Turing complete program - but common ones are simply containing a string of a URL.
Edit: I was loosely involved in some of the conversation around smart contract and token implementation on a top 10 chain and there’s actually a lot of interesting issues with on chain data, such as if child pornography is added suddenly in some countries hosting a node can be seen as distributing CP (so only allowing URLs and then having filters to remove that at a community level is an easy solution).
I currently only like NFTs as representations of digital licenses or tickets etc anyway, so simple hashes work for me.
Edit: I was loosely involved in some of the conversation around smart contract and token implementation on a top 10 chain and there’s actually a lot of interesting issues with on chain data, such as if child pornography is added suddenly in some countries hosting a node can be seen as distributing CP (so only allowing URLs and then having filters to remove that at a community level is an easy solution).
I currently only like NFTs as representations of digital licenses or tickets etc anyway, so simple hashes work for me.