Proof of History is a consensus mechanism used in blockchain technology, primarily associated with the Solana network. It allows for the verification of the order and passage of time between events on the blockchain, ensuring that transactions are recorded in a secure and efficient manner. By creating a historical record that proves that an event has occurred at a specific time, Proof of History enhances the speed and scalability of the network. This method reduces the need for nodes to communicate constantly, allowing them to focus on validating transactions and maintaining the integrity of the blockchain.