Blockchain is a decentralized, distributed ledger technology that securely records transactions across multiple computers. Each transaction is grouped into blocks, which are linked in a chronological chain. This ensures transparency, security, and immutability, as altering any block would require changing all subsequent blocks across the entire network. Blockchain is the backbone of cryptocurrencies like Bitcoin, but its applications extend to supply chain management, finance, healthcare, and more. By eliminating the need for intermediaries, blockchain fosters trust, reduces costs, and enhances efficiency in various industries.