An NFT is a Non-Fungible Token. The token refers to a digital token or certificate that is stored on a secure distributed database referred to as the blockchain. NFTs are therefore unique digital assets that can be bought and sold, with every transaction being permanently recorded in the blockchain. One way to think about NFTs is that they are like a certificate of authenticity that is permanently embedded into a database, along with any future transactions that transfer ownership. You can see who minted the NFT, who bought it and so on, in perpetuity. NFTs are a new technology, and we are only seeing a small portion of their likely future potential.
You may have heard of blockchain before, as it is the underlying concept behind decentralized cryptocurrencies like Bitcoin and Ethereum. Not all blockchains currently support NFTs, as this is an evolving technology and each blockchain has different structures. Ethereum is the most widely used blockchain service for NFTs, but this may change over time. NFTs can be used to represent both tangible and intangible items, but the current news has centered on how they have been used to sell purely digital / intangible items such as gifs and other digital artwork. Non-fungible refers to the lack of interchangeability of tokens; each one is purely unique. This differs from fungible assets that can be interchangeable with others of equal value, such as cash.