Ledger is a secure, distributed digital ledger technology that is used to record and store transactional data. It is a type of database that is shared across a network of participating nodes, and offers tamper-proof and immutable storage of records. Ledger technology is used to track and record transactions in a variety of industries, including banking, finance, healthcare, government, and supply chain management. There are two main types of Ledger technology: permissioned and permissionless. Permissioned Ledgers are those that are kept by a single entity or organization, and only those with permission can view and write to the ledger. Permissionless Ledgers are decentralized, public ledgers such as the Bitcoin blockchain, which can be accessed by anyone.