Blockchain protocols are sets of rules and standards that govern how data is transmitted and validated across a blockchain network. They ensure that all participants in the network can agree on the state of the data, enabling secure and transparent transactions. Different protocols can vary in their consensus mechanisms, which determine how transactions are verified and added to the blockchain. Common examples of blockchain protocols include Bitcoin, which uses a proof-of-work system, and Ethereum, which has transitioned to a proof-of-stake model. These protocols play a crucial role in defining the functionality, security, and efficiency of the respective blockchains they support.