ERC stands for Ethereum Request for Comment. For any technical improvements of smart contract standards, an ERC request is proposed. ERC20 is the technical standard of smart contracts for implementing a token on the Ethereum blockchain; 20 is the number of the proposal request. There are multiple steps an ERC goes through to become a standard. An ERC request is first drafted, and then goes through iterations to be updated, accepted, or finalized to become a final Ethereum Improvement Proposal (EIP). You can find all of the standard ERC requests that has been converted into EIPs on GitHub at https://github.com/ethereum/EIPs/tree/master/EIPS.
Before moving further, let's understand the difference between a coin and a token:
- Coin: A native digital asset or cryptocurrency of a blockchain is called a coin...