Oracle
An oracle delivers real-world information (prices, weather, delivery status) to smart contracts, which cannot see anything outside the blockchain by themselves.
Explained simply
A smart contract only knows what is in the blockchain. It does not know the euro-dollar rate or whether a shipment has arrived. Someone has to feed that data in: the oracle.
Because a single data provider could be manipulated, reputable oracles aggregate many independent sources and publish the average. Faulty oracle data has caused several DeFi losses in the past.
From the familiar world
The fixing price on the exchange: it is derived from many sources and serves as the binding reference price for contracts that refer to it. The oracle is the price broker for smart contracts.
An example
A crop insurance as a smart contract pays out automatically when a weather oracle reports less than 20 millimetres of rain in 60 days for a region. No claim form, no assessor.
Why it matters
Oracles are the seam between blockchain and reality. Their quality decides whether an application is reliable. For tokenised securities, for example, they supply interest rates and prices.
To pass on
„A smart contract is blind to the outside world. The oracle is its news service.“
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