$ETH Ethereum (ETH) is a decentralized blockchain platform that supports smart contracts and decentralized apps (dApps). Launched in 2015 by Vitalik Buterin, it's the second-largest cryptocurrency after Bitcoin. Ethereum transitioned to Proof-of-Stake in 2022 to improve energy efficiency and scalability. It's widely used in DeFi, NFTs, and Web3 development.