Ethereum is a public and open-sourced blockchain-based platform created by Vitalik Buterin that features smart contracts. Generally seen as what is referred to as Blockchain 2.0, because it is used to create & power applications that are outside the realm of being solely an accounting method for digital currencies. A good example, to quickly understand the difference, is that the technology that powers Saturn Network runs on Ethereum but it would not be possible to run this same technology on Bitcoin.
Ethereum is currently the largest decentralized software platform that is capable of supporting smart contracts, and as a result Distributed Applications (dApps). It would be wrong to simply define Ethereum as a cryptocurrency or to confuse it with Ether, which is a cryptocurrency part of the Ethereum system. Ethereum is intended to be used as a platform that provides users with a way to build programs without any involvement of middlemen, this means those programs are less exposed to the abuses by those middlemen or authorities.
The platform went live on July 30, 2015 and currently is the second major currency on the market with over 45 billion dollars of capitalization. In terms of the future, the latest news around Ethereum is mostly focused on the move to Serenity which is one of the last major development phases where we will see a change of Ether mining’s concept from Proof-of-Work to Proof-of-Stake with the idea to reduce the power cost of the process.