LINK(Chainlink) is a general-purpose framework for building decentralized oracle networks that give smart contracts access to secure and reliable data inputs and outputs. Each decentralized oracle network consists of independent node operators. In the Chainlink network, each node verifies the accuracy of external real-world data, aggregates them using an agreed-upon method, and delivers them to smart contracts that requested for the data.

This helps makes smart contracts useful for entities like financial institutions, decentralized finance projects, agricultural companies, or any data-driven companies. LINK is a utility token used to pay for data queries and is soon to be used as collateral for service agreements.
 

More information here https://chain.link/