Distributed Ledger is as a decentralized data structure that store data on many devices across the network.

It has three basic components:

Data model:  Is a current state of the distributed ledger. It consists of the ledger of records called transactions.
 Transaction:  Is an action that changes the current state of the data model. A transaction can be a record of an asset transfer among parties involved in Distributed Ledger system.
Consensus: Defining which transaction should be accepted and in what order to keep all parties data structures in the identical state. It defines how parties agree on a true state of the distributed ledger.

Distributed Ledger Network Architecture

 

Most web applications utilizing a client-server network architecture, with multiple clients depending on centralized server or servers for computational power and data resources. Communication between clients routed by a centralized hub as well.
DLT implements distributed peer-to-peer network architecture. In Peer-to-peer (P2P) networks, clients connected directly to each other without the central hub. Each peer contributes to the network computing power an data storage capacity. P2P networks considered to be more secure and stable as they do not have a central point of attack or single point of failure.

Distributed Ledger Access Type

 

Permissionless or public DL allow anyone to join the P2P network and authorize all participants to submit the transaction without verifying their identity.
Permisshened or private DL requires user verification to access P2P network. In private DL networks parties first agrees to do business with each other. Submitting transaction on the private DL network requires user permissions verification.