A ledger is a record-keeping tool that systematically tracks financial transactions or other types of data exchanges in an organized manner. In traditional accounting, a ledger serves as the central repository where all changes in financial accounts are documented, usually in a double-entry format that ensures the books are balanced. In this system, every transaction affects at least two accounts, providing a check-and-balance mechanism that helps prevent errors and fraud. With the advent of digital technology, ledgers have evolved beyond paper-based or simple digital spreadsheets to include more complex, decentralized systems like blockchain. A blockchain ledger, for example, is distributed across multiple nodes in a network and uses cryptographic techniques to secure and validate transactions. Whether physical or digital, centralized or decentralized, the fundamental purpose of a ledger remains the same: to provide a transparent, auditable, and authoritative record of transactions, enabling accountability and facilitating analysis.