Blockchain is a decentralized, distributed digital ledger technology that records transactions across multiple computers in a way that is secure, transparent, and tamper-resistant. As an academic concept and research field, it investigates methods for achieving distributed consensus, maintaining data integrity without a central authority, and enabling verifiable, immutable record-keeping through cryptographic linking of data blocks. Its significance lies in enabling trustless systems for transaction processing and data management, fostering research into novel economic models, governance structures, and applications across diverse domains where data provenance and immutability are critical.