Ethereum is a decentralized, open-source blockchain platform that enables the creation and execution of smart contracts. It was proposed in late 2013 by Vitalik Buterin and formally launched in July 2015. Ethereum introduced a significant innovation by introducing a Turing-complete programming language called Solidity, which allows developers to build and deploy decentralized applications (DApps) on the Ethereum blockchain.

Unlike Bitcoin, which primarily serves as a digital currency, Ethereum aims to provide a decentralized platform for various applications beyond just financial transactions. It enables developers to create smart contracts, which are self-executing contracts with predefined rules and conditions. Smart contracts automatically execute transactions or actions once the specified conditions are met, eliminating the need for intermediaries.

Ethereum operates using its native cryptocurrency called Ether (ETH). Ether is used as a means of compensation for participants who perform computational tasks on the network, known as "gas." Gas fees are paid by users to cover the cost of executing smart contracts and running decentralized applications on the Ethereum network.

One of the key features of Ethereum is its ability to support the development of decentralized applications and tokens through its ERC-20 token standard. ERC-20 tokens are built on top of the Ethereum blockchain and have become the industry standard for creating new tokens for Initial Coin Offerings (ICOs) and crowdfunding campaigns.

Ethereum has undergone several major upgrades throughout its history, with the most significant one being Ethereum 2.0. This upgrade aims to transition Ethereum from a proof-of-work (PoW) consensus mechanism to a more energy-efficient proof-of-stake (PoS) mechanism. The transition to Ethereum 2.0 will address scalability issues, reduce transaction costs, and increase the network's overall efficiency.

Ethereum has gained widespread adoption and has become the platform of choice for many blockchain projects, decentralized finance (DeFi) applications, and non-fungible tokens (NFTs). It has a vibrant and active developer community, and its open nature allows anyone to participate and contribute to its ecosystem.