What is an ERC-721 NFT standard? What is the meaning definition of ERC 721? Difference between ERC 721 and ERC 1155 - What does ERC stand for?

What is an ERC-721 NFT standard? What is the meaning definition of ERC 721?

NFTs or non-fungible tokens are literally tokens. A token on the blockchain that can be uniquely identified. The Ethereum NFTs have adopted mainly two methods to create NFTs. The ERC 721 and the ERC 1155. 

What is the difference between the ERC 721 and the ERC 1155?

Both the ERC 721 and the ERC 1155 are types of NFTs or tokens. Each type of token creation are known as standards. The ERC 721 standard NFT and the ERC 1155 standard NFT. Each standard creates a set of rules to follow. 

What is the ERC 20? 

ERC stands for Ethereum Rule for Comment. ERC 20 is the token standard most widely use on Ethereum for creation of tokens that are fungible. Similar to how fiat currencies work. A $20 bill can be exchanged for another $20 bill with no difference to each user. The same applies for ERC 20 tokens. They are mostly used for this purpose. NFTs mostly use the ERC 721 or ERC 1155 standard because they are non-fungible.

NFTs can be created in many different standards on the blockchain. ERC 721 NFTs are a type of standard for non-fungible tokens. ERC 721 NFTs allow each unique token (NFT) to be identified and transferred individually.  

ERC 1155 NFTs differ from ERC 721 by the ability to create classes or sets of assets in comparison to the ERC 721 which only ties to a single asset. ERC 721 does not allow batch transfers. Where as ERC 1155 NFTs do allow for batch transfers. The difference can become very costly when comparing 721 vs. 1155. 

ERC 1155 are able to do what ERC 20 and ERC 721 NFTs are able to do and more. Thus most of the newer NFT collections created after 2019 have adopted the ERC 1155 standard. 

The ERC 1155 standard NFT also allows for a semi-fungible token.  It supports the conversion of fungible tokens to NFTs and vice versa.