ERC-721 defines an interface for non-fungible tokens, or NFTs, in which each token has its own identifier and recorded owner. One contract can manage an entire collection. Token ID 7 in one contract is not the same asset as token ID 7 in another.
Ownership and transfer controls
Applications can query a token's owner, transfer it and inspect permissions. A holder can approve an address for one NFT or authorize an operator to manage all their NFTs in that contract. Collection-wide approval can therefore affect more than the item currently being viewed.
What safe transfer checks
The safeTransferFrom mechanism checks that a receiving smart contract implements the expected NFT reception behavior. This helps avoid certain incompatible-contract transfers. The word safe does not certify the recipient's intentions, the collection's authenticity or the transfer's economic value.
Media and rights are separate
An optional metadata extension provides information through a token URI. Images and descriptions may be stored outside the blockchain, and their references may be changeable. Owning the token does not automatically grant copyright or ownership of a represented physical object. Those rights depend on applicable terms and law; ERC-721 itself specifies the token interface.