NFTs stand for non-fungible tokens—tokens that can’t be substituted for something else. For example, your $1 bill is valued the same as any other $1 bill and can be substituted for any $1 bill in the world. This makes it fungible.
A Van Gogh art painting, on the other hand, is one of a kind, and can’t be substituted for another painting by the same painter or another artist. It is non-fungible.
An NFT proves the ownership of a non-fungible asset like digital art, credentials, badges, and more.