Ethereum, represented by the symbol ETH, is a decentralized, open-source blockchain platform that enables the creation of smart contracts and decentralized applications (DApps). Launched in 2015 by Vitalik Buterin, Ethereum has become the second-largest cryptocurrency by market capitalization, right after Bitcoin.

Ethereum's primary innovation is its ability to execute smart contracts, which are self-executing agreements with the terms of the agreement directly written into code. This allows for the creation of various decentralized applications, such as decentralized finance (DeFi) platforms, non-fungible tokens (NFTs), and more. Ethereum has a native cryptocurrency called Ether (ETH), which is used to power transactions and smart contracts on the network.