(This is a brief summary of Ethereum's white paper)
Ethereum is a new cryptocurrency, like Bitcoin or Litecoin, that adds a number of new features. Most notably the inclusion of Agents (also known as Contracts); Independent Turing-complete programs that exist on the Ethereum blockchain. These Agents can receive Ether (Ethereum's currency) and other inputs, perform computations, hold balances, transfer Ether, and even activate other Agents.
Ethereum also attempts to fix some current issues with cryptocurenncy mining, such as rise of specialized hardware, large mining pools that aim to control the network, and the lack of reward for stale blocks, dissuading miners with weaker hardware.
