Ethereum is a decentralized, open-source blockchain system that features smart contract functionality. It was conceived in 2013 by programmer Vitalik Buterin @vitalik.eth and development began in early 2014 through a Swiss company, Ethereum Switzerland GmbH (EthSuisse).

Ethereum allows developers to write smart contracts, which are self-executing agreements where the terms are directly written into code. These contracts run on the Ethereum Virtual Machine (EVM), ensuring transparency and trust in their execution.