An immutable ledger refers to a record-keeping system where data entries cannot be altered or deleted once they are added. This characteristic is fundamental to how blockchain technology operates.When transactions occur, they are grouped into blocks and added to a chain. Each block is linked to the previous one, creating a chronological order of all transactions. This structure ensures that any attempt to modify a previous entry would require changing not just that entry but all subsequent blocks, which is extremely difficult due to the consensus mechanisms in place.The immutability of the ledger enhances security and trust. Users can confidently verify past transactions without worrying about tampering. This is crucial for maintaining the integrity of digital assets, as it helps prevent fraud and ensures transparent record-keeping.Overall, the concept of an immutable ledger serves as a foundational principle for many decentralized applications, enabling trust and accountability without the need for a central authority.