ETC is a coin that is related to the history of Ethereum. (can be viewed as an old Ethereum). A hard fork of Ethereum happened in July 2016 due to an attack, known as the DAO attack, that hacked around 50 million dollars. Main community supporters including Vitalik proposed to change the code of Ethereum to invalidate the hack and refund the victims. However, some held the belief that the code of a blockchain should be immutable no matter what. It happened that the community later agreed on a hard fork, which birthed Ethereum classic