Blockchain Oracle Leader: LINK
The problem with current blockchains is that each one is a closed world, only capable of processing data within its own network. Data outside of this world is beyond their understanding and not considered within their realm.
To address this issue, the blockchain oracle was created!
An oracle is a tool that provides real-world data to the blockchain world. Chainlink is a leader in the blockchain oracle space, capable of linking real-world data and most blockchain data, allowing blockchains to transition from closed systems to open ones.
Typically, data stored on a blockchain is considered "on-chain data," while data outside of the blockchain is considered "off-chain data," and the two cannot communicate.
Therefore, each blockchain is a closed network that cannot interact with external data (including other blockchains and the real world). For example, smart contracts are independent of other blockchains or the real world.
Suppose there are three blockchains, A, B, and C. For A blockchain, the A blockchain data equals on-chain data (previously unique and independently existing in the A blockchain). The data from B and C blockchains and the real world equals off-chain data (previously impossible to integrate/interact with A blockchain).
The oracle serves as the bridge that allows the A blockchain to simultaneously access data from B, C blockchains, and the real world! In this field, Chainlink can be considered a leader and a giant.
For example, well-known DeFi protocols or smart contracts such as Aave, yearn.finance, and Crypto.com rely on Chainlink to provide real-world data and data from other blockchains.
Chainlink's website: https://chain.link