What is a Chainlink price feed?

An on-chain reference contract, maintained by a decentralized network of Chainlink nodes, that publishes an aggregated real-world price (like ETH/USD) for other contracts to read.

Nodes each fetch the price from many exchanges, agree on a median off-chain, and publish it on-chain; your contract just reads the latest answer. It solves the oracle problem without a single trusted source, updating on a deviation threshold or heartbeat interval.