NFTs stand for “Non-fungible token”, essentially unique, tokens that are “one of a kind”. These are often minted in limited quantities, and cannot be copied or replicated on the block chain. While there can be printed/digital copies – the original NFT exists on the blockchain.
A physical example of this would be someone owning a copy of the Mona-Lisa. It looks like the original, but its value is worth only the paper and ink used to print it. The original, protected in Louvre museum, holds the value of the artwork. NFTS are like this, but in digital form.