Ethereum is an open source blockchain platform that allows developers to build and deploy smart contracts and decentralized applications (DApps). It was created by Vitalik Buterin and others in 2015 and aims to be a general blockchain platform that provides a wider range of functions than just digital currencies like Bitcoin.

Here are some key features of Ethereum:

1. Smart Contracts: Ethereum introduced the concept of smart contracts, which are computational codes that automatically execute contract conditions. This enables developers to create a variety of applications on the blockchain, ranging from decentralized financial services to digital identity verification.

2. Ether (ETH): Ethereum’s native cryptocurrency is Ether (ETH). It is the primary way to exchange value and make payments on the Ethereum network.

3. Decentralized Applications (DApps): Ethereum supports the development of decentralized applications. These applications run on the Ethereum blockchain, are powered by smart contracts, and can interact with each other through Ether.

4. ERC-20 and ERC-721 standards: Ethereum introduced token standards such as ERC-20 and ERC-721, enabling developers to create and issue their own tokens for various purposes, including crowdfunding and representation of digital assets.

5. Blockchain Upgrades: Ethereum has undergone multiple upgrades to improve performance, security, and functionality. Some of the important upgrades include Homestead, Metropolis, Constantinople, and Istanbul.

Ethereum's goal is to provide an open, global, permissionless and censorship-free computing platform that provides developers and users with more innovative possibilities. This makes Ethereum one of the important platforms in the blockchain and cryptocurrency field.