Price Feed (Data Feed)
A continuously updated stream of off-chain data — most commonly asset prices — delivered to smart contracts by oracle networks. Price feeds aggregate data from multiple sources and exchanges, apply outlier detection, and deliver tamper-resistant reference prices. They are critical infrastructure for DeFi lending (determining liquidations), derivatives (settlement prices), and any smart contract that needs to know real-world asset values.
“Chainlink's ETH/USD price feed aggregates prices from over 20 data sources and is updated by a decentralized network of nodes, making it extremely difficult for any single entity to manipulate.”
Oracle
A service that provides external, off-chain data to smart contracts, which by design cannot access any information outside their blockchain. Oracles bridge the gap between on-chain and off-chain worlds, supplying critical data like asset prices, weather conditions, sports scores, and random numbers. The 'oracle problem' — ensuring the oracle itself is trustworthy — is typically solved through decentralization, economic incentives, and data source aggregation.
Chainlink (LINK)
The largest decentralized oracle network, providing tamper-resistant external data (price feeds, weather data, random numbers, and more) to smart contracts across multiple blockchains. Chainlink solves the 'oracle problem' — the challenge of getting reliable off-chain data on-chain — through a decentralized network of node operators who are economically incentivized to provide accurate data through staking and reputation systems.
Liquidation
The forced closing of a leveraged position or the seizure and sale of collateral when a borrower's position falls below the required margin or collateralization ratio. In DeFi lending, liquidation occurs automatically via smart contracts when the value of collateral drops below a protocol-defined threshold, protecting lenders from bad debt.
DeFi (Decentralized Finance)
An ecosystem of financial services built on blockchain networks that operate without traditional intermediaries like banks, brokerages, or insurance companies. DeFi uses smart contracts to provide lending, borrowing, trading, insurance, derivatives, and yield generation in a permissionless, transparent, and composable manner. Anyone with a wallet can participate.