Public blockchains are open to anyone and allow any person to participate as a node, validate transactions, and contribute to the network's security. Examples include Bitcoin and Ethereum. Private blockchains, on the other hand, are restricted networks where access is limited to a specific group of participants. They are often used by businesses to maintain privacy and control over the transaction and validation process, making it easier to comply with regulations. Private blockchains typically have a centralized authority that manages the network, distinguishing them further from their public counterparts.