Chainlink is a decentralized 'oracle' service for smart contracts written in to blockchains. Since blockchains cannot access data outside their network, 'oracles' are required to execute smart contracts which rely on outside data. Chainlink creates a market for these external data feeds and a way for smart contracts to access this 'off-chain' data. While smart contracts are touted as a highly reliable method for executing a contract based on pre-defined conditions, that execution is only as reliable as the data which is fed in to the contract. Chainlink seeks to increase the quality and accuracy of data fed in to smart contracts through their market-based mechanisms.