What is Blockchain

In order to understand blockchain ,let us start by understanding what is a block.

A block is basically a record.

A receipt is a record of items bought. A birth certificate is a record of your details at birth. An ID card is a record of your belonging to country.

A block is a record!

Here is an example of a block.

block in a blockchain
Screenshot from blockchain.com

Just like all the other records I have just mentioned a block has 3 primary items

  1. Data
  2. Hash of the block
  3. Hash of the previous Block


Data is the information about the record eg. the initiator of the transaction, the recipient of the transaction, the purpose of the transaction. Let us take the case of a bitcoin block. Some of the data in a bitcoin block is

  • the number of bitcoin being sent
  • the sender ,the receiver
  • and the number of transactions being made.

If we have a blockchain for property the data on the transaction would be

  • The owner /seller
  • The buyer
  • Payment details eg. Morgage , cash etc.
data in the block
Screenshot from blockchain.com


The hash of the block is a unique ID . This is like a fingerprint. There is no other block has the same identity as the other. It is a unique identity of a particular block.

Screenshot from blockchain.com

Previous Hash

Previous hash of the block. It acts as the Reference or pointer to the previous block hence producing a block Chain.

previous hash of the block
Photo screenshot from btc.com


Therefore , a blockchain is a digital record of transactions which are linked together in single list, called a chain.

screenshot from udemy

What else would you like to know about the blockchain?

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