What is a Distributed Ledger?

Distributed Ledger
A distributed ledger (also called a shared ledger, or referred to as distributed ledger technology) is a consensus of replicated, shared, and synchronised digital data geographically spread across multiple sites, countries, or institutions. There is no central administrator or centralised data storage.
A peer-to-peer network is required as well as consensus algorithms to ensure replication across nodes is undertaken. One form of distributed ledger design is the blockchain system, which can be either public or private. But not all distributed ledgers have to necessarily employ a chain of blocks to successfully provide secure and valid achievement of distributed consensus: a blockchain is only one type of data structure considered to be a distributed ledger.
What are some of the real case uses?
According to the Harvard Business Review, Blockchain (the technology behind Bitcoin and other cryptocurrencies) is “an open, distributed ledger that can record transactions between two parties efficiently and in a verifiable and permanent way”. Thus, majority of cryptocurrencies can be used as an example of distributed ledgers.
Nowadays, banks are investing heavily in distributed ledgers as a cost-saving measure and a way to reduce operational risks. The future use of distributed ledgers is expected to monetise the Internet of Things in a programmable economy.
Moreover, Everledger is used to track diamonds by recording numerous unique data points.