Ethereum is the foundational smart-contract blockchain and the home of decentralized finance. Launched in 2015, it introduced programmable money through the Ethereum Virtual Machine (EVM) — now the industry-standard execution environment copied by dozens of other chains. Ethereum holds the largest total value locked in DeFi and is the settlement layer for the majority of stablecoins, lending markets and decentralized exchanges.
In 2022 Ethereum transitioned from Proof of Work to Proof of Stake ("The Merge"), cutting its energy use by ~99.9% and enabling staking yield on ETH. Its roadmap is "rollup-centric": rather than scaling the base layer directly, Ethereum pushes activity to Layer-2 rollups (Arbitrum, Base, Optimism) that inherit its security while offering far lower fees.
ETH is both the gas token and the primary collateral asset across DeFi. With deep liquidity, the most audited contracts and the strongest developer ecosystem, Ethereum remains the benchmark against which every other smart-contract chain is measured.