Ethereum is a decentralized blockchain platform that enables smart contracts and decentralized applications (DApps) to be built and operated without any downtime, fraud, control, or interference from a third party. It was proposed by Vitalik Buterin in late 2013 and development began in early 2014, with the network going live on July 30, 2015.

Ethereum's native cryptocurrency is called Ether (ETH), which is used to pay for transaction fees and computational services on the network. Ethereum is considered one of the most important blockchain platforms due to its versatility and ability to support a wide range of applications beyond just financial transactions.

One of the key features of Ethereum is its ability to execute smart contracts, which are self-executing contracts with the terms of the agreement between buyer and seller directly written into lines of code. This eliminates the need for intermediaries and ensures the contract is fulfilled as programmed.