Bitcoin is a decentralized digital currency, without a central bank or single administrator, that can be sent from user to user on the peer-to-peer bitcoin network 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 in 2008 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.
As of February 2015, over 100,000 merchants and vendors accepted bitcoin as payment. Bitcoin can be purchased on online exchanges and traded for traditional currencies.
The blockchain is a public ledger that records bitcoin transactions. A novel solution accomplishes this without any trusted central authority: maintenance of the blockchain is performed by a network of communicating nodes running bitcoin software. Transactions of the form payer X sends Y bitcoins to payee Z are broadcast to this network using readily available software applications. Network nodes can validate transactions, add them to their copy of the ledger, and then broadcast these ledger additions to other nodes. The blockchain is a distributed database – to achieve independent verification of the chain of ownership of any and every bitcoin amount, each network node stores its own copy of the blockchain.
Approximately six times per hour, a new group of accepted transactions, called a block, is created, added to the blockchain, and quickly published to all nodes, without requiring central oversight. This allows bitcoin software to determine when a particular bitcoin amount has been spent, which is necessary in order to prevent double-spending in an environment without central oversight. Whereas a conventional ledger records the transfers of actual bills or promissory notes that exist apart from it, the blockchain is the only place that bitcoins can be said to exist in the form of unspent outputs of transactions.[3]:ch. 5.
Bitcoins are mined with powerful computer hardware and software. A maximum of 21 million Bitcoin will be available, after which no further bitcoins will be produced.
The algorithm which governs the production of Bitcoin limits the quantity that will be produced, and the rate at which they will be produced. It is a finite commodity – there is a fixed amount, and that ensures that greater demand will always prop up the price. In this way, it is similar to other finite commodities such as crude oil.