A blockchain ledger is a decentralized database that records transactions across multiple computers securely. Each block in the chain contains a list of transactions, a hash of the previous block, and a timestamp, ensuring chronological integrity and resistance to tampering. This technology functions on the principles of cryptography and consensus algorithms, allowing participants to agree on the validity of the data without needing a central authority. Its distributed nature enhances security and transparency, making it valuable for applications beyond cryptocurrencies, such as supply chain management and smart contracts.