Ethereum is a decentralized blockchain protocol designed to execute Smart Contracts and build decentralized applications (dApps) on a distributed computing platform. Ethereum uses the internal cryptocurrency Ether (ETH) as a means of payment for transaction processing, which is handled by participating computers.
The Ethereum-Whitepaper was published in late 2013 and the project was officially announced at a Bitcoin conference in early 2014. Vitalik Buterin, co-founder of Ethereum, began designing the protocol due to some limitations in the Bitcoin protocol.
Ethereum was officially launched in mid-2015 with the informally stated goal of supporting “unstoppable applications.” The Ethereum Foundation, founded in 2014, is an Ethereum-focused nonprofit organization dedicated to research, core protocol development, and Ethereum ecosystem growth. The Ethereum Foundation also oversaw the Ether crowdsale in July 2014.
The current Ethereum Blockchain (ETH) was forked from the original Ethereum Classic Blockchain (ETC) in a “hard fork” on July 20, 2016. This hard fork was initiated after a bug in the smart contract of Ethereum’s Decentralized Autonomous Organization (DAO), which resulted in 3.6 million Ether being stolen. Since then, both blockchains have continued to operate under their respective names.
In the summer of 2020, momentum returned to the Ethereum network with “Decentralized Finance” (DeFi) and the transaction volume even exceeded that of the Bitcoin blockchain.
You can find a detailed article on Ethereum here.