Ethereum is a decentralized smart contract platform that acts as a global computer, enabling developers to build dApps, DeFi protocols, NFTs, and DAOs. Unlike Bitcoin’s limited scripting, Ethereum introduced the Ethereum Virtual Machine (EVM), a Turing-complete execution environment that allows complex logic through smart contracts. With the 2022 Merge upgrade, Ethereum transitioned from Proof-of-Work to Proof-of-Stake (PoS), reducing energy consumption by 99% and enabling staking-based network security. It features EIP-1559 fee burning, making ETH potentially deflationary, while Layer-2 rollups like Optimism, Arbitrum, and zkSync scale the network by providing faster and cheaper transactions. Ethereum remains the leading hub for DeFi (Uniswap, Aave), NFTs (Bored Ape Yacht Club, OpenSea), and token standards like ERC-20, ERC-721, and ERC-1155. Its modular roadmap with sharding and zk-rollups aims to solve scalability, security, and decentralization (the blockchain trilemma), solidifying Ethereum as the settlement layer of the decentralized economy.