A blockchain is a decentralised storage of any form of data, that is immutable. New data is added to the chain frequently by the users of this network. The data is stored in the form of blocks, where each block is linked to a previous block through a cryptographic hash, timestamp, and the data itself.
How is it immutable?
Can’t someone just delete a block in the blockchain, and poof! remove it or modify it? Yes they can. But wait, listen to the complete story.
The Blockchain is distributed, in the sense, the same copy of the blockchain is copied to each and every user of the network. So, if a person has to delete a record in the entire blockchain, then he/she has to attack more than 50% of the users who are a part of the blockchain, all at the same time! Getting it?
Ex: If there are 10 users. If I want to hack and remove a block or modify it in the blockchain, I will have to hack any 6 users at the same time, delete the block, so that the remaining network will think that it has faulty blocks, and will copy itself from the other 6 users. But this is not computationally easy. So, the security of any blockchain network increases with an increase in the number of users.
This is one of the reasons why we can find many networks initially trying to gather users and having Test phases. The more users there are, the more secure the network.
What is the use of it?
What is the use of being a part of the blockchain?
Every network has it’s own purpose out there. These networks reward their users with their own Coins. You would have heard about Bitcoin, Ethereum, XRP, and a lot of others.
These coins are used to purchase services in the marketplace, for transactions between two entities and also can be traded for currency.
Once data is stored in the blockchain, it can never be erased, so this can be used to store transactional data, important documents, and more.