Oracles

In this chapter we discuss oracles, which are systems that can provide external data sources to Ethereum smart contracts. The term “oracle” comes from Greek mythology, where it referred to a person in communication with the gods who could see visions of the future. In the context of blockchains, an oracle is a system that can answer questions that are external to Ethereum. Ideally oracles are systems that are trustless, meaning that they do not need to be trusted because they operate on decentralized principles.