Remember your favorite toy LEGO Blocks. Connecting LEGO blocks and creating a chain. Block chain can be imagined something similar. In online world these blocks are transactional information written by different users around the world. These Blockchain stores tons of information across network of personal computers making it not only de-centralised and secure. We can also say that Blockchain is a digital ledger in which transactions made in bitcoin or another cryptocurrency are recorded chronologically and publicly.
Blockchain technology is quite old yet is revolutionary concept for our future as it is increasing getting used in varied field like banking, cyber-security, Insurance , Research and many other fields. Each block contains secured information, once all transaction are complete, it creates another block that is linked with references the proceeding block and more transactions that will be currently happening, all the way back to the beginning of the network to what is known as the genesis block. These blocks (information) are secured by decentralized consensus. It means any change in one block can only be made when all the owners/ users are in consensus. A Block basically contains data , hash and hash of previous block. Data includes sender & Receiver online address and amount, hash is unique code that all users have to approve and hash of previous block. Now, it is near to impossible to temper with any of the blocks because if one blog is changed the whole block chain technology will collapse. Been such a secure information tunnel it is used famously for Bitcoin Transaction.
Another feature is blocks are de-centralised. It has Peer to Peer Network. Any new user joins, he gets access to all the blockchain. New block (say for Bitcoin transactions) is formed after 10minutes. All the users will have access to it. They will verify the block then only the block is complete and then next block is started.
Many industries are rapidly understanding the implications of Blockchain and how it can help companies and end customer. Now only the data is secure, it is faster , cheaper and surely the future.