What is a Blockchain?
In general a blockchain is defined as a distributed system which records and stores transaction records. Blockchain more specifically is defined as a shared, immutable record of peer-to-peer transactions built from linked transaction blocks and stored in a digital ledger.
Blockchain is also similar to a database which stores information, however the main difference is that the data is located in a network of personal computers called nodes where there is no central entity such as a government or bank controlling the data.
Instead, all data is shared publicly although the contents of each data is only accessible to those with permission. Below is a diagram to illustrate how information is stored in distributed network compared to a centralised and decentralised network.
Figure 1: Illustration of network comparisons between distributed ledgers, centralised and decentralised networks. (Blockgeeks)