Ethereum is an open-source, public, blockchain-based distributed computing platform and operating system featuring smart contract (scripting) functionality. It supports a modified version of Nakamoto consensus via transaction-based state transitions.
Example: Ethereum is used to build decentralized applications (dApps) that run on the Ethereum blockchain. These applications can be used to facilitate peer-to-peer contracts, create digital tokens, and more. For example, an individual can create a smart contract on the Ethereum blockchain that enables them to buy and sell digital assets with other people without the need for a third-party intermediary.