Non-Funglible Tokens are the tokens that are pegged to a specific item and cannot be replaced by another token. Each of the NFT tokens is unique and has no analogs.
For example, if you want to tokenize a work of art, you have to create a special coin that cannot be replaced. NFT is stored in the blockchain as your property. The most famous example of using such tokens is the CryptoKitties game, where every digital kitten has its price.