According to its creators, Ethereum is the first "programmable blockchain" in the world, making it possible for it to function as a virtual market place for software, games, and, most significantly, financial services. All of this is built on Ether, a cryptocurrency that serves as the Ethereum network's payment mechanism. Due to its decentralized structure, it offers total protection against theft and fraud. I think I was able to address your question about "What is Ethereum?". In any case, you can get additional information about this here.
