What is “Blockchain”
A blockchain is a public ledger wherein all Bitcoin transactions are recorded. It is growing constantly with ‘completed blocks’ adding up as more and more miners are mining the Bitcoins. The blocks are added to the blockchain in a linear, chronological order. Each time a block gets completed, a new block is generated. There are countless number of such blocks in the blockchain. So are the blocks randomly placed ? No, they are linked to each other (like a chain) in proper linear, chronological order with every block containing a hash of the previous block.
Once entered, information can never be erased. All records in the bitcoin blockchain are verifiable records of every single bitcoin transaction ever made.
Blockchain | how it works
Each node (computer connected to the Bitcoin network using a client that performs the task of validating and relaying transactions) gets a copy of the block chain, which gets downloaded automatically upon joining the Bitcoin network.
The block chain has complete information about the addresses and their balances right from the genesis block to the most recently completed block.
It is this technology of blockchain that has made Bitcoin decentralised. Due to this technology, no manipulations of blocks or faulty transactions of Bitcoins are possible. Today this technology is finding place in many other areas such as Medicine and Insurance.