Blockchain is a digital ledger technology that securely records transactions across a network of computers. Each transaction is grouped into a 'block,' which is linked to previous blocks, forming a chronological 'chain.' This decentralized structure makes it nearly impossible to alter or forge records, ensuring transparency and trust without the need for a central authority. Blockchain is widely used in cryptocurrencies like Bitcoin, but its transparent and tamper-resistant nature also supports applications in supply chain management, voting systems, and digital identity verification.