What is a Distributed Ledger?

Ledgers, the foundation of accounting, are as ancient as writing and money.

Their medium has been clay, wooden tally sticks (that were a fire hazard), stone, papyrus and paper. Once computers became normalized in the 1980s and '90s, paper records were digitized, often by manual data entry.

These early digital ledgers mimicked the cataloguing and accounting of the paper-based world, and it could be said that digitization has been applied more to the logistics of paper documents rather than their creation. Paper-based institutions remain the backbone of our society: money, seals, written signatures, bills, certificates and the use of double-entry bookkeeping.

Computing power and breakthroughs in cryptography, along with the discovery and use of some new and interesting algorithms, have allowed the creation of distributed ledgers.

More info here: https://www.coindesk.com/information/what-is-a-distributed-ledger/