Distributed Ledger Technology (DLT)
In short: Distributed ledger technology (DLT) is a way of keeping a ledger that is accessed by multiple participants and stored in multiple locations at once.
Distributed ledger technology (DLT) is a way of keeping a ledger that is accessed by multiple participants and stored in multiple locations at once. It is the basis of blockchain technology.
Why it matters
DLT is the umbrella category, and a blockchain is one specific design within it: records are grouped into blocks, and each block is linked to the previous one by a cryptographic hash. So every blockchain is a DLT, but not every DLT is a blockchain; some designs use other data structures, such as directed acyclic graphs. The building blocks are shared across the category: copies of the data on many nodes, a peer-to-peer network, a consensus mechanism, and digital signatures. Together they let participants agree on one record without a central operator who keeps the master copy.
Example
Two banks settle payments with each other. Traditionally each keeps its own ledger, and staff compare the two at the end of the day to find mismatches. On a shared distributed ledger, both banks write to and read from the same record, so there is only one version of each payment to agree on and far less reconciliation work.