NFT

An NFT (non-fungible token) is a blockchain token that is individually unique, unlike interchangeable tokens such as ETH, and is used to prove ownership of items like art, game assets or passes. ethereum.org's NFT page explains that NFTs are individually unique and provably scarce, unlike fungible tokens such as ETH or USDC where every unit is identical, and that ownership of each one is publicly verifiable on the blockchain. Quest platforms use them too: Galxe hands out NFTs as rewards, and its tasks can check whether a wallet holds a given NFT.

NFTs are also a scam vector. ethereum.org describes airdrop scams that drop an NFT or token into your wallet to lure you to a fake claim site. NFT approvals are broad as well: revoke.cash explains that setApprovalForAll() lets a contract move every NFT in a collection. See token approval and allowlist.