Non-Fungible Tokens, commonly known as NFTs, are digital assets that reside on a blockchain. They exist natively in "token" form on the blockchain, but they are different from other "tokens" such as Bitcoin and Ethereum because NFTs are non-fungible (ie. not interchangeable). If you and your friend both exchange 1 BTC with each other, you both still end up with 1 BTC - they are fungible, so the end result is the same. However, the end result is not the same if you were to each exchanging 1 NFT - the end result would not be the same. It would be like exchanging limited edition baseball cards - they are baseball cards, but they represent different players.
Here at 5D, our NFTs are unique digital artworks and scarce digital assets. Often, they may even be redeemable for a physical representation of the artwork, created and produced by the artist themself. This additional feature depends on the NFT and the artist.