Ethereum is a decentralized blockchain platform that enables developers to build and deploy decentralized applications (dApps) on its network. Ethereum's native cryptocurrency, Ether (ETH), is used to pay for transaction fees and computational services on the network. Ethereum uses a proof-of-work (PoW) consensus algorithm to validate transactions and add new blocks to the blockchain. This means that miners compete to solve complex mathematical problems to validate transactions and earn rewards in the form of Ether.

Ethereum's PoW algorithm has been criticized for its high energy consumption and scalability issues. To address these concerns, Ethereum is currently transitioning to a proof-of-stake (PoS) consensus algorithm, which will reduce energy consumption and increase scalability. The transition to PoS is expected to be completed in 2022 with the launch of Ethereum 2.0. Despite these challenges, Ethereum has become one of the most popular blockchain platforms for building dApps and has a vibrant developer community.