In blockchain, oracles serve as intermediaries that bring external data to smart contracts. The terms "push" and "pull" refer to how data is delivered from the oracle to the blockchain.

A push oracle mechanism involves the oracle actively sending (or "pushing") data to the smart contract at predefined intervals or when specific conditions are met. This method is often used when the smart contract requires real-time or frequent updates, such as in price feeds for decentralized finance (DeFi) platforms. For example, an oracle might push the latest cryptocurrency prices to a smart contract every minute.

In contrast, a pull oracle mechanism works by having the smart contract request (or "pull") data from the oracle only when needed. The smart contract initiates the data retrieval process, which is useful when the information is required on-demand rather than continuously. This approach can be more efficient in scenarios where data is needed less frequently or where it's critical to avoid unnecessary data transmission, saving on gas fees and reducing network congestion.

The choice between push and pull mechanisms depends on the specific requirements of the smart contract, such as the need for real-time data versus cost-efficiency. Both methods offer different advantages depending on the use case and the nature of the data required.