Chainlink

Chainlink is a decentralized oracle network that aims to connect smart contracts with data from the real world. It was launched in 2017 by Sergey Nazarov and Steve Ellis. Chainlink sits on top of blockchain platforms like Ethereum and serves as a middleware between on-chain and off-chain systems.

A key problem for smart contracts on blockchains is that they can't natively access off-chain data (data that is outside of the blockchain). But for many use cases, they need such data to execute their terms. Examples of this data can be price feeds, event outcomes, weather data, and other kinds of API data.

Chainlink aims to solve this problem by creating a decentralized network of "oracles" that can provide reliable data to smart contracts. An oracle is a third-party information provider that supplies data to blockchains. The decentralization of oracles in Chainlink's network is important because it reduces the risk of data manipulation and single points of failure.

Chainlink uses LINK, an ERC-677 token, to incentivize nodes in its network to provide accurate data. A contract creator uses LINK to pay for services on the Chainlink network.

Chainlink is one of the most widely used oracle networks in the DeFi (Decentralized Finance) ecosystem. It's particularly known for supplying reliable price feeds to DeFi applications, but the applications of Chainlink are potentially vast - any smart contract that requires real-world data could benefit from Chainlink's services.