Ledger currency is a unit of value whose balances exist as entries in a ledger kept by a single issuer or operator, as distinct from a blockchain currency, whose ledger is replicated across many computers and updated by consensus.
The issuer of a ledger currency records who holds what, settles transfers by updating its own books, and sets the rules for issuance and redemption. The Linden Dollar in 📝Second Life is a well-known example: 📝Linden Lab maintains the ledger and operates an exchange where users trade Linden Dollars for U.S. dollars. Airline miles, loyalty points, and most in-game currencies follow the same pattern. 📝Resonance Dollars, a currency recording contributions to a cooperative, were designed as one.
Bitcoin is the defining contrast. Its ledger has no central keeper, which removes the need to trust an issuer but adds cost, latency, and technical complexity. A ledger currency gives up that independence in exchange for simplicity, speed, and the ability to correct mistakes, and it depends on participants trusting the organization that keeps the books.
Second Life was a ledger currency. Resonance Dollars are a ledger currency. Bitcoin is a blockchain currency, and 📝blockchain just adds complexity early, unnecessarily.