Ethereum is a decentralized blockchain platform that enables the creation and execution of smart contracts and decentralized applications (DApps). It was proposed by Vitalik Buterin in late 2013 and launched in July 2015. Ethereum is often referred to as the world's second-largest cryptocurrency by market capitalization, after Bitcoin.

The Ethereum blockchain operates using a cryptocurrency called Ether (ETH). Ether serves as both a digital currency and a fuel for running smart contracts and powering decentralized applications on the Ethereum network. It is used to pay for transaction fees and computational services on the platform.

One of the key innovations of Ethereum is its ability to support the development of smart contracts. Smart contracts are self-executing agreements with predefined rules and conditions. They automatically execute and enforce the terms of the contract without the need for intermediaries. Smart contracts enable a wide range of applications, including decentralized finance (DeFi), supply chain management, gaming, and more.

The Ethereum blockchain is built upon a decentralized network of computers, known as nodes, which collectively maintain and secure the network. The nodes store a copy of the entire blockchain and validate transactions and smart contracts.

Ethereum has undergone several upgrades to improve scalability, security, and functionality. The most significant upgrade is Ethereum 2.0, also known as Ethereum's Serenity phase. It aims to transition the network from a proof-of-work (PoW) consensus mechanism to a proof-of-stake (PoS) mechanism, enhancing scalability and energy efficiency.

Overall, Ethereum has had a profound impact on the blockchain and cryptocurrency industry, providing a robust platform for the development of decentralized applications and fostering innovation in the field of blockchain technology.