Ethereum Classic is a decentralized network that supports smart contracts. It was created by Vitalik Buterin in 2013. Following the DAO hack in 2016, several members of the Ethereum community rejected the idea of a hard-fork to revert transactions (and return funds to the DAO participants), leading to the split between Ethereum and Ethereum Classic.
Ethereum Classic (ETC) parted away from Ethereum at block 1,920,000 (July 20th 2016) to retain the original version of the network, reinforcing the blockchain’s core characteristic of immutability. Since its ICO in 2015, Ethereum has relied on Proof of Work (PoW); Ethereum Classic shares its early history with its first (common) block being mined in July 2015.
Like Ethereum, the network is fueled by a cryptocurrency named ether (classic). It comprises an open-source, globally decentralized computing infrastructure, which executes programs called smart contracts.
Similarly, Ethereum Classic is based on an account model to record state changes. It relies on the Ethereum Virtual Machine (EVM) with two types of addresses: externally owned addresses (EOAs) and contract addresses that are deployed on the EVM.
As of March 2020, Ethereum Classic’s hashrate is much lower than Ethereum’s and the level of on-chain activity is also inferior to Ethereum's. With Ethereum planning to part away from Proof-of-Work (to introduce PoS with ETH 2.0), Ethereum Classic plans on persisting as the immutable Proof of Work version of Ethereum.