Ethereum is a decentralized blockchain platform launched in 2015 by Vitalik Buterin that extends beyond digital currency by enabling smart contracts and decentralized applications, allowing developers to build programmable financial services, games, and digital assets without intermediaries, using its native cryptocurrency Ether to pay for transactions and computational services, transitioning from energy-intensive proof-of-work to proof-of-stake consensus to improve scalability and sustainability, supporting a vast ecosystem of decentralized finance protocols, non-fungible tokens, and layer-two solutions, facing challenges like network congestion and high fees, yet remaining the foundation for innovation in Web3 and blockchain technology worldwide.