A non-fungible token (NFT) is a specialized type of cryptographic token representing something unique, like a domain name, a limited-time skin for a video game, or other digital properties owned by a user. Therefore the NFTs are not mutually interchangeable, meaning an individual might trade ownership of a domain name for ownership of a rare character skin or a cryptocurrency. NFTs differ from cryptocurrency, NFTs are entirely non-fungible, and they cannot be traded for something identical. Cryptocurrency is fungible and is exchanged for something that is of equal or identical value.
NFTs are used to create digital ownership and scarcity. It develops a possibility of interoperability across multiple platforms through blockchain, which acts as the management layer of NFT. Blockchain allows the exchange of an item from one party to another and provides for the NFTs to be displayed in various eBay style marketplaces. NFTs are used in specific applications to acquire unique or rare digital items like crypto art, crypto-collectibles, and crypto-gaming.

CryptoPunks by LarvaLabs and traded on Ethereum
Blockchain had early use in the art industry, allowing individuals to own digital intellectual property with records stored in the digital blockchain roster. NFTs are used to prove ownership and authenticity of digital art. In June of 2017, a company called Larva Labs released an art collectors line called CryptoPunks. The “Punks” were available free of cost for anyone with an Ethereum wallet. Only 10,000 Punks were developed, no two alike, and all were quickly claimed. Ethereum wallet holders may now sell or trade punks for Ethereum coins. The average punk sold for approximately 4.12E, which equated to $2,998 on December 29, 2020. CryptoPunks is just one example of rare digital art.
Blockchain games also use NFTs, for example, CryptoKitties, a game developed by a Canadian company called Axiom Zen. The game allows users to use the Ethereum blockchain to represent in-game assets controlled by the user instead of the developer. In-game assets for CryptoKitties can be traded in third-party marketplaces requiring no added permissions from the developer.
There are various standards for non-fungible tokens, and the standards are what make NTFs valuable to consumers. Standards give developers a guarantee that the non-fungible assets will behave in a particular way and exactly describe how they will interact with the basic functionality of the specific asset.
The ERC-721 is a standard developed by the CryptoKitties developer, Axiom Zen, and was also the first standard that represented non-fungible assets. The ERC-721 standard is an inheritable Solidity smart contract, which means other developers can use the ERC-721 to create and develop new compliant contracts that fit their assets using the import tool from the OpenZepplin library. ERC-721 provides permissions to transfer non-fungible assets from one party to another and provides an identifier for that asset’s present owner.

ERC-721 transfer codes and owner0f operations

Example of an ERC-1155 token contract
Enjin developed the ERC-1155 standard. It is used primarily in selling classes of assets, meaning if a user has a wallet with 500 shields in it, the user may sell off all 500 shields at once instead of selling them individually. By allowing the sale of an entire class of items, ERC-1155 provides an increased efficiency from the ERC-721 standard where each item has a unique identifier, even if the item is a duplicate. The downside to ERC-1155 is a loss of information. Due to the bulk sale of items, the history of ownership from one party to the next cannot be tracked for individual shields.
Composables are developing out of the ERC-998 standard, which provides a template for NFTs to own both non-fungible and fungible assets.
Non-fungible token marketplaces
Decentraland
Decentraland is an informal NFT marketplace, described as a fully decentralized digital world –like virtual reality. The users can purchase plots of land (non-fungible unique digital assets) that they can develop upon.
Enjin Marketplace
Enjin is the official marketplace for Enjin based NFTs. It allows users to discover, buy, and sell NFTs from the web-based interface and also the native Enjin wallet.
OpenSea
OpenSea focuses on every type of non-fungible token. It allows users to sell art, game items, collectibles, virtual stuff, domain names, etc.
Rarible
Rarible offers minting and marketplace services for NFTs. It also has a governance token called RARI, which allows users to participate in voting on important matters. The users can keep the minted NFTs, gift them, and sell them on the marketplace.
Super Rare
Super rare, as the name states, deals in super rare art. It’s an NFT marketplace that deals with unique digital art-works.
Non-fungible and blockchain gaming
0xUniverse
0xUniverse is a blockchain space strategy where you build spacecraft, launch exploratory efforts, find new worlds and trade with other discoverers.
Blankos Block Party
Blankos Block Party is an open-world multiplayer game styled like a block party. It focuses on custom art and design, building, exploration, and curating collections of unique and rare Blankos.
CryptoKitties
CryptoKitties is a blockchain game on Ethereum developed by Canadian studio Axiom Zen that allows players to purchase, collect, breed and sell virtual cats.
CSC - Space MMO
CSC | Space MMO. CSC is a casual space MMO with fast-paced combat, a player economy, and an uncapped crafting system.
Decentraland
Decentraland is an informal NFT marketplace, described as a fully decentralized digital world –like virtual reality. The users can purchase plots of land (non-fungible unique digital assets) that they can develop upon.
Hash Rush
Hash Rush is a real-time strategy game that allows gamers to compete with each other for cryptocurrency and other rewards such as new skins and boosts.
My Crypto Heroes
My Crypto Heroes is a turn-based battle game. Players gather historical heroes, level them up, acquire extensions, and aim to be at the top of the Crypto World.
THE SANDBOX
Users may buy, sell, and trade their voxel creations on secondary markets and truly become a part of this user-built world where everything you see is built by and for the community.
Non-fungible digital art collections
CryptoArte
CryptoCelebrities
CryptoPunks
Rarible
Timeline
People
Further reading
5 Examples of Non-Fungible Tokens (NFTs) | Sequence
Web
August 25, 2020
Non-Fungible Tokens (NFT): Beginner's Guide
Melanie Kramer
Web
November 9, 2020
The Role of Non-Fungible Tokens in Art | Grit Daily News
Joel Comm
Web
November 30, 2020
Token Models: Fungible vs. Non-Fungible
Kaleido Servies
Web
What's this Non-Fungible Token (NFTs) Craze All About, Anyway?
Veronica Morozova
Web
November 5, 2020
Documentaries, videos and podcasts
An Introduction to Non-Fungible Tokens (NFTs)
August 29, 2020
Fungible vs non-fungible tokens on the blockchain - 0xcert - Medium
April 26, 2018
NFT crypto (Non fungible token) with Layah Heilpern
November 10, 2020
Non-Fungible Tokens (NFT): Beginner's Guide
November 9, 2020
Tokenizing Our Virtual Future: A Deep Dive Into Non-Fungible Tokens | Hacker Noon
September 13, 2020