Public and private blockchains differ primarily in accessibility, control, and use cases. A public blockchain is open to anyone, allowing anyone to join, participate, and validate transactions. It is fully decentralized, with no single entity in control, and relies on consensus mechanisms like proof-of-work (PoW) or proof-of-stake (PoS) to maintain security and integrity. Examples include Bitcoin and Ethereum, which are transparent and permissionless, making them ideal for applications requiring trustlessness and decentralization.

In contrast, a private blockchain is restricted and controlled by a single organization or consortium. Access is limited to authorized participants, and the governing entity oversees permissions, rules, and consensus mechanisms. This centralized control makes private blockchains more efficient and scalable, as they do not require extensive computational power for validation. They are often used by businesses for internal processes, such as supply chain management or record-keeping, where privacy and control are prioritized.

While public blockchains emphasize transparency and decentralization, private blockchains focus on efficiency, privacy, and regulatory compliance. Public blockchains are suited for open, trustless environments, whereas private blockchains cater to organizations needing secure, controlled networks. Both have unique advantages, and the choice depends on the specific requirements of the application or industry.