ERC20 tokens are the most common type of token built on top of Ethereum. They are fungible in nature, meaning that there isn’t a distinction between individual tokens. For example, if I have 100 metal marbles in my hand that are all the same size and color, it doesn’t matter which one I give you. In the same way, if I have 100 of the same ERC20 token, it doesn’t matter which one I give you. This contrasts with ERC721 tokens which are non-fungible tokens (NFTs) such as cryptokitties.

Ethereum⌗

Fungible Tokens⌗

Fungible Tokens, aka ERC20 tokens. Fungible means each one is the same of them, like the coins you are used to buy something in the supermarket.

Non-Fungible Tokens(NFTs)⌗

Non-Fungible Tokens, aka ERC721 tokens, Non-Fungible means each one is different from others. Like some old money that worth more than its face, and you won’t and even can’t use it to buy some thing in supermarket.