The person who tries to solve a computationally difficult puzzle to win the bitcoin is called ‘bitcoin miner’. When a miner joints the bitcoin network, he gets a copy of the blockchain – downloaded automatically. This blockchain is a shared public ledger in the form of a database that contains information about all Bitcoin transactions so far executed. (A ledger is a record of all financial transactions in a systematic manner).
The mission of the bitcoin miner is to solve the software generated cryptographic puzzle. If he became successful, he will add a block into the blockchain besides winning the bitcoin. But solving the puzzle require a highly powerful computer system with a high bandwidth network connection. New blocks will be added with new successful miners solving the puzzle and winning bitcoin. Remember every block contains the same information about the whole transactions in the network and is updated frequently with each new transaction.
What is more important about blockchain is that it is a distributed network. This means that all data are updated with all members with each development. Each block contains the whole previous transaction records in digital format. Each block is chained with the next block; so it is called blockchain. If a new block comes, it will be updated in every block very quickly.
Now, our hero is not the bitcoin; but the blockchain- the technology behind bitcoin. Blockchain is sequential transaction databases. As a distributed network, blokchain contains complete information about the addresses and their balances (of the networked people) right from the starting of the blockchain and distributes it among all the members.