A public blockchain is a permissionless, decentralized ledger open to all. Participants can read, write, and validate transactions—through mining or staking—on networks like Bitcoin, Ethereum, or Solana. These systems prioritize openness, censorship resistance, and community-driven governance, with trust secured by consensus mechanisms. Public blockchains power cryptocurrencies, DeFi, NFTs, and open Web3 services. While offering transparency and decentralization, they also face scalability and privacy limitations, which are addressed by emerging layer-2 protocols and privacy-enhancing techniques.