Bitcoin block-chain technology.

Blockchain technology

Blockchain  formation. 
   The main chain{black} consists of the longest series of blocks from the genesis block {green} to the current block. Orphan blocks {purple} exist outside of the main chain.

Network data.

A Blockchain originally Block chain, is growing list of records, called BLOCKS.
 Blocks is linked using cryptography.
Blockchains which are readable by public, are widely used by cryptocurrencies. Private blockchains have been proposed for business use. Some marketing of blockchains has been called "snake oil".

Eachblock contains a Cryptographic hash of the previous block a time-stamp and transaction data. It is an open distributed ledger that can record transactions between two parties effeciently and in a verifiable and permanent way. For use as a distributed ledger, a blockchain is typically managed by a peer-to-peer network collectively adhering to a protocol for inter-node communication and validating new blocks. Once recorded,the data in any given block cannot be altered retroactively without alteration of all subsequent blocks, which requires consensus of the network majority.
 Through blockchain records are not unalterable, blockchains may be considered secure by design and exemplify a distributed computing system with high Byzantine fault tolerance. Decentralised consensus has therefore been claimed with a blockchain.

Blockchain was invented by Sathoshi Nakamoto in 2008 to serve as public transaction ledger of the Cryptocurrency bitcoin. The invention of blockchain for bitcoin made it in  the first digital currency to solve the double-spending problem without the need of a trusted authority or central server.