In the context of cryptocurrencies like Bitcoin, the ledger is public, meaning it's open to the public and anyone can check and verify the transactions. This ledger, also known as a "blockchain", is essential in providing transparency and trust in the system. All transactions are bundled into "blocks" that are chained together to form the "blockchain". Once a block is added to the blockchain, it's virtually impossible to alter it, making the ledger highly secure against fraud and hacking.
Apart from the public ledger, there are also private ledgers used by some cryptocurrencies and other digital platforms. Private ledgers are controlled by a central authority and are not open for anyone to view or verify. They're ideal for businesses that want to use blockchain technology while maintaining complete control over their transaction data.
Regardless of being a public or private ledger, they both play a crucial role in confirming and recording all transactions within a cryptocurrency network. They consequently serve the critical purpose of ensuring that the same digital currency cannot be spent more than once by the same user, enhancing the overall security and stability of the cryptocurrency.