Non-fungible vs fungible Tokens ?ERC20 = each token is SIMILAR - 1 bitcoin = 1 bitcoin and 1$=1$
ERC-721 NFT = each token is UNIQUE - 1 diamond isnt equal to another diamond
Non-Fungible Tokens are used to create verifiable digital scarcity.
ERC-721 and NFT ?ERC-721 is a free and open standard, describing how to build NFT on the Ethereum blockchain. While most tokens are fungible (like bitcoin), non-fungible tokens are all unique and therefor rare and one-of-a-kind collectables.
With a sensational entrance in the blockchain world - notably with the success of cryptokitties (already 25 million dollars and some rare sold for 250 ETH) - the NFT market is in full expansion!
But NFT are not exclusive to cryptocollectibles like cryptokitties.
Thanks the constant development of the blockchain ecosystem, the properties of ERC-721 tokens allow applications in many fields like gaming, digital arts, software licenses, advertising or even hotel boooking
Read more about this booming market: https://medium.com/auctionity/beyond-cryptokitties-pushing-future-usages-of-erc-721-and-nft-1b56a1460ce7