A distributed ledger (also called a shared ledger, or referred to as distributed ledger technology) is a consensus of replicated, shared, and synchronized digital data geographically spread across multiple sites, countries, or institutions. There is no central administrator or centralised data storage - wikipedia 
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.
In 2016, numerous banks tested distributed ledgers for international payments.