Blockchain is a chain of blocks that are connected together. It is a decentralized system which means it is not controlled by a single organization. It is a shared and a permanent database shared among nodes on a network. The blockchain stores information in a way that makes it very difficult or impossible to change or modify.

Nodes

Since we know that the blockchain consists of numerous amount of data and this data is stored on these nodes. Every node keeps a copy of the previous node in the form of unique ID's known as Hashes. A hash itself is basically a numeric value that is used to validate the authenticity of different types of inputs. These hash values can be in different length sizes, from 160-512 bits.

Before we dive into the concept of Decentralization, it is necessary to understand what a things work in a centralized system.

Centralized System

In a centralized system, the database consists of a single server into which all the data is stored. So it's safe to say that all the data resides at a single location and all the applications must retrieve data from that location.

Decentralized System

If we were to compare the centralized way of storing data to decentralization in the blockchain, We could say that since the data is stored on a peer to peer network of nodes, The blockchain is a decentralized system. It also removes the barrier of relying on a central authority.

What is a peer to peer network?

A peer to peer network (P2P) connects nodes directly without the need of a centralized server or a third party, Nodes on a P2P network are typically located near each other and run similar protocols.