The execution environment of an Ethereum blockchain is special in that it does not allow the program to interact with the outside world. This is necessary to guarantee that any time the program, aka the smart contract, is executed it always yields the same result. This is called determinism which is a critical design attribute for blockchains.
If a smart contract needs to interact with the outside world, a component called oracle is necessary. There are different designs for an oracle machine. Chainlink is a prominent player in the marketplace that supports a wide range of industries and data endpoints. Details of the Chainlink design can be found here. A technical explanation of how the different components in the blockchain, DApps and Chainlink work together can be found on our blog site: https://kaleido.io/blog.
Kaleido's Chainlink service will set up a Chainlink network by joining together Chainlink node instances provisioned by different members of the Kaleido environment and configure them to use a common set of LinkToken contract and Oracle contract. Samples are also provided to demonstrate how to develop the client smart contract to interact with the Oracle contract, and how to develop DApps code to integrate the Chainlink flow into user experiences.