It took him 13 years to add all those squares
BBC:
[
What is an NFT?
NFT stands for non-fungible token.
In economics, a fungible asset is something with
units that can be readily interchanged - like money.
With money, you can swap a £10 note for two £5 notes
and it will have the same value.
However, if something is non-fungible, this is impossible - it means it has
unique properties so it cannot be interchanged
with something else.
It could be a house, or a painting such as the Mona Lisa, which is one of a kind.
You can take a photo of the painting or buy a print but there
will only ever be the one original painting.
NFTs are "one-of-a-kind" assets in the digital world
that can be bought and sold like any other
piece of property, but they have no tangible form of their own.
The digital tokens can be thought of as certificates
of ownership for virtual or physical assets.]
https://www.bbc.co.uk/news/technology-56371912
https://en.wikipedia.org/wiki/Non-fungible_token
