A blockchain protocol is a set of rules and standards that govern the operation of a blockchain network. It defines how transactions are verified, added, and secured within the blockchain, ensuring integrity and transparency. These protocols utilize cryptographic techniques to maintain a distributed ledger that is immutable and decentralized, allowing participants to have a shared and tamper-resistant record of transactions. Examples include Bitcoin and Ethereum protocols, which have distinct features and consensus mechanisms, enabling different applications within financial services, supply chains, and beyond.