BITCOIN

Bitcoin (₿) is a cryptocurrency, a form of electronic cash. It is a decentralized digital currency without a central bank or single administrator Bitcoins can be sent from user to user on the peer-to-peer Bitcoin network directly, without the need for intermediaries. Transactions are verified by network nodes through cryptography and recorded in a public distributed ledger called a blockchain. Bitcoin was invented by an unknown person or group of people using the name Satoshi Nakamoto^[9] and released as open-source software in 2009. Bitcoins are created as a reward for a process known as mining. They can be exchanged for other currencies, products, and services. Research produced by the University of Cambridge estimates that in 2017, there were 2.9 to 5.8 million unique users using a cryptocurrency wallet, most of them using bitcoin.
Bitcoin has been criticized for its use in illegal transactions, its high electricity consumption, price volatility, thefts from exchanges, and the possibility that bitcoin is an economic bubble Bitcoin has also been used as an investment, although several regulatory agencies have issued investor alerts about bitcoin.

Blockchain

Network nodes can validate transactions, add them to their copy of the ledger, and then broadcast these ledger additions to other nodes. To achieve independent verification of the chain of ownership each network node stores its own copy of the blockchain. About every 10 minutes, a new group of accepted transactions, called a block, is created, added to the blockchain, and quickly published to all nodes. This allows bitcoin software to determine when a particular bitcoin was spent, which is needed to prevent double-spending without central oversight. A conventional ledger records the transfers of actual bills or promissory notes that exist apart from it, but the blockchain is the only place that bitcoins can be said to exist in the form of unspent outputs of transactions.The blockchain is a public ledger that records bitcoin transactions. It is implemented as a chain of blocks, each block containing a hash of the previous block up to the genesis block^[of the chain. The maintenance of the blockchain is performed by a network of communicating nodes running bitcoin software.^:215–219 Transactions of the form payer X sends Y bitcoins to payee Z are broadcast to this network using readily available software applications. Nevertheless, the "trustless" design requires "each and every user to download and verify the history of all transactions ever made, including amount paid, payer, payee and other details."