In the crypto sphere, ledger or DLT (Distributed Ledger Technology) is a way of storing information across multiple locations and accessible by multiple participants. This distributed but unified database is the Ledger.

It has become common for people to have servers in their homes. Let's say that you have a house with a large family, consisting of six rooms. Furthermore, over the years, you have archived hundreds of movies and TV shows, accounting for dozens of terabytes of data. To make that content accessible from a single point for all residents, it would be easy to connect the server to TVs of each room.

Moreover, any other type of data would be accessible simultaneously for all rooms. However, there is a huge vulnerability with this network model. If that single server fails, the entire network is down. Even worse, the data files could be irreversibly corrupted.

To avoid this, Distributed Ledger Technology is used to spread out the data across many servers. Each server not only contains the complete copy of all the data, but any change from a single access point is then synced up across all other servers on the network. This leads us to the key difference between DLT and blockchain.

While blockchain is a type of DLT, DLT is not blockchain. After all, DLT doesn't require a consensus algorithm to work, either Proof-of-Work or Proof-of-Stake. Furthermore, DLT doesn't require a chain of data blocks to work. For these reasons, DLT is more scalable and faster, but it is less secure because it doesn't require transaction confirmations.

To understand this key difference, let's consider why Bitcoin has never been hacked. Each data block is cryptographically chained with a 256-bit SHA algorithm, and all of the blocks are distributed across tens of thousands of nodes (computers). On top of that, the blockchain PoW consensus ensures that those nodes validate all transactions, i.e., the change of the Ledger.

In order for that record to be tampered with, one would have to take over 51% of nodes. That itself is a virtual impossibility, given the sheer amount of computation power employed by that number of nodes. Therefore, while blockchain is a type of ledger, it is more oriented towards security rather than speed and scalability.