Ethereum is a decentralized blockchain platform, launched in 2015 by Vitalik Buterin and his colleagues. It allows the development and deployment of smart contracts and decentralized applications (DApps) without the need for intermediaries. 
The Ethereum network uses the Proof of Stake (PoS) consensus mechanism through the Ethereum 2.0 upgrade, which improves performance and reduces energy consumption compared to the previous Proof of Work (PoW). The main currency of the network is Ether (ETH), which is used to pay transaction fees (gas fees) and as collateral in DeFi applications. 
Ethereum is an important platform in the fields of decentralized finance (DeFi), NFTs and Web3, with a large and constantly growing ecosystem.