About Chainlink
From Chainlink Community Wiki
The Chainlink Network is a protocol that supports the creation of decentralized oracle networks that enable data feeds, off-chain computation, and cross-chain messaging on and between blockchain networks. The oracle nodes are run by Chainlink Node Operators (NOPs)—independent entities responsible for deploying onto new blockchain networks, sourcing high-quality data, and providing highly secure off-chain services to consumers with high uptime and reliability. [1]
When Chainlink launched on May 30, 2019, the protocol supported a single ETH/USD Price Feed secured by three oracle nodes.