A blockchain is the chain of blocks that contain information. This technique was originally described in 1991 by a group of researchers and was originally intended to timestamp digital document so that it’s not possible to backdate them. It was later adapted by Satoshi Nakamoto in 2009 to create the digital Cryptocurrency Bitcoin.
In technological terms, Blockchain is a distributed ledger that is completely open to anyone. Once some data has been recorded inside a blockchain it becomes very difficult to change it.
Each block contains three parts, some data, the hash of blocks and the hash of previous blocks. The data that is stored inside a block depends on the type of blockchain. The hash of blocks is just like fingerprints. It identifies a block and all of its contents and it is always unique, just as a fingerprint. Once the block is created, its hash is being calculated. If you want to detect any changes in blocks, it is necessary to calculate the hash. The third part called as the hash of the previous block effectively creates a chain of blocks and this technique makes a blockchain so secure.
Blockchain has something called as Proof of Work (POW). It is a mechanism that slows down the creation of new blocks. It mitigates tampering of blocks.
Apart from hashing and POW, blockchain also secure them by being distributed. Instead of using a central entity to manage the chain, blockchain use the peer-to-peer network and anyone is allowed to join. When someone joins the network, he gets the full copy of blockchain.
One of the recent developments in blockchain is the creation of smart contracts. These contracts are simple programs that are stored on the blockchain and can be used to automatically exchange coins based on certain conditions.
As of now, 19 industries have been disrupted by blockchain. Some of those are:-
Banking and payments, Cyber security, Supply chain management, Forecasting, Networking and Internet of things (IoT), Insurance, Private transport and ride sharing, Online data storage, Charity, Voting, Government.