Ethereum

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.

Before you can understand ethereum, it helps to first understand the internet.
Today, our personal data, passwords and financial information are all largely stored on other people’s computers – in clouds and servers owned by companies like Amazon, Facebook, or Google. Even this article is stored on a server controlled by a company that charges to hold this data should it be called upon.
This setup has a number of conveniences, as these companies deploy teams of specialists to help store and secure this data, and remove the costs that come with hosting and uptime.
But with this convenience, there is also vulnerability. As we’ve learned, a hacker or a government can gain unwelcome access to your files without your knowledge, by influencing or attacking a third-party service – meaning they can steal, leak or change important information.
Brian Behlendorf, creator of the Apache Web Server, has gone so far as to label this centralized design the “original sin” of the Internet. Some like Behlendorf argue the Internet was always meant to be decentralized, and a splintered movement has sprung up around using new tools, including blockchain technology, to help achieve this goal.

Ethereum is one of the newest technologies to join this movement.

While bitcoin aims to disrupt PayPal and online banking, ethereum has the goal of using a blockchain to replace internet third parties — those that store data, transfer mortgages and keep track of complex financial instruments.
Ether is a fundamental cryptocurrency for operation of Ethereum, which thereby provides a public distributed ledger for transactions. It is used to pay for gas, a unit of computation used in transactions and other state transitions. Mistakenly, this currency is also referred to as Ethereum.[45] It is listed under the code ETH and traded on cryptocurrency exchanges, and the Greek uppercase Xi character (Ξ) is generally used for its currency symbol. It is also used to pay for transaction fees and computational services on the Ethereum network