Blockchain 

A blockchain is a kind of distributed ledger technology (DLT) that is made up of an expanding list of data, known as blocks, that are safely connected to one another using encryption. Each block includes transaction information, a timestamp, and a cryptographic hash of the preceding block (generally represented as a Merkle tree, where data nodes are represented by leaves). The timestamp demonstrates that the transaction data was there at the moment the block was produced. Each block links to the blocks before it, forming an effective chain (compare linked list data structure), because each block carries information about the blocks preceding it. Thus, once a transaction has been recorded, it cannot be undone without also undoing all subsequent blocks, making blockchain transactions irreversible.

A peer-to-peer (P2P) computer network commonly manages blockchains for use as a public distributed ledger, where nodes collectively abide by a consensus algorithm protocol to add and validate new transaction blocks. Blockchains may be deemed secure by design and serve as an example of a distributed computing system with strong Byzantine fault tolerance even if blockchain data can still be changed and forks are a possibility. 

Based on earlier work by Stuart Haber, W. Scott Stornetta, and Dave Bayer, a person (or group of individuals) going by the name (or pseudonym) Satoshi Nakamoto constructed a blockchain in 2008[6] to operate as the public distributed ledger for bitcoin cryptocurrency transactions. [7] Bitcoin was the first digital money to eliminate double spending without the aid of a central server or trusted authority because of the blockchain technology within it. Other applications have been influenced by the bitcoin design and publicly viewable blockchains, which are extensively utilised by cryptocurrencies. One kind of payment rail may be thought of as the blockchain.