A public blockchain is a type of blockchain that is open to anyone to participate and view. It is decentralized and maintained by a network of nodes that validate transactions and store a copy of the ledger. Public blockchains, such as Bitcoin and Ethereum, are transparent and trustless, meaning that they do not require participants to trust each other or a central authority.

On the other hand, a private blockchain is a type of blockchain that is permission, meaning that only certain individuals or organizations have access to participate and view the network. Private blockchains are often used by businesses and organizations for internal purposes, such as tracking supply chain logistics or managing sensitive data. Private blockchains are typically centralized, with a single entity controlling the network.

The main difference between public and private blockchains is the level of accessibility and control. Public blockchains are open and transparent, allowing anyone to participate and view the network, while private blockchains are permissioned and controlled by a single entity. While public blockchains are often associated with cryptocurrencies and trustless systems, private blockchains are more commonly used in enterprise settings for specific purposes.