I asked this question last month in the MPSIMS thread about Melania Trump selling NFTs. Snowboarder_Bo provided links to some previous threads discussing NFTs.
Also there is this MPSIMS thread with a link to a 2 hour video that is probably more than you would ever want to know about NFTs. (Honestly, I only got through about 45 minutes but feel like I had a pretty good grasp of the idea by then.)