Chainlink is a cryptocurrency that aims to encourage a global network of computers to provide reliable, real data for smart contracts running on blockchains. The problem is that most smart contracts have to rely on some external data source to properly execute their conditions. For example, smart contracts seeking replication of bonds or insurance contracts may require access to APIs that report market prices or IoT data.
Chainlink was created to solve this problem by encouraging data providers (called "oracles") to act as a bridge between blockchain smart contracts and external data sources. Each oracle in Chainlink is encouraged to provide accurate data as each is assigned a reputation rating. Moreover, when the nodes adhere to the software rules and provide useful data, they are rewarded in the LINK cryptocurrency.
From 2020, Chainlink try to support all blockchain-based smart contract networks.