It is a token format in the Ethereum network. Most tokens in circulation today run on this standardized format.
Ethereum is currently the second most valuable cryptocurrency. Ethereum enables you to create smart contracts or ERC-20 tokens on its blockchain network.
It is a cryptocurrency that was forked from the Ethereum cryptocurrency. If cryptocurrencies have a similar name, it means they are two different cryptocurrencies.
There is a website where you can search for a public address in the network and find out how much ETH is at that address, or how many other ERC-20 tokens are stored at that address within the ETH network.