Bitcoin
Bitcoin is a worldwide cryptocurrency and digital payment system called the first decentralized digital currency, since the system works without a central repository or single administratorIt was invented by an unknown programmer, or a group of programmers, under the name Satoshi Nakamoto and released as open-source software in 2009. The system is peer-to-peer, and transactions take place between users directly, without an intermediary. These transactions are verified by network nodes and recorded in a public distributed ledger called a blockchain.Besides being created as a reward for mining, bitcoin 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 also be held as an investment. According to research produced by Cambridge University in 2017, there are 2.9 to 5.8 million unique users using a cryptocurrency wallet, most of them using bitcoin. On 1 August 2017 bitcoin split into two derivative digital currencies, the classic bitcoin (BTC) and the Bitcoin Cash (BCH).

Blockchain


The blockchain is a public ledger that records bitcoin transactions. A novel solution accomplishes this without any trusted central authority: the 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, a block, is created, added to the blockchain, and quickly published to all nodes. 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.

Bitcoin Faucet
Bitcoin faucets are a reward system, in the form of a website or app, that dispenses rewards in the form of a satoshi, which is a hundredth of a millionth BTC, for visitors to claim in exchange for completing a captcha or task as described by the website. There are also faucets that dispense alternative cryptocurrencies.Rewards are dispensed at various predetermined intervals of time. Faucets usually give fractions of a bitcoin, but the amount will typically fluctuate according to the value of bitcoin. Typical payout per transaction is less than 1000 satoshi,[note 1] although some faucets also have random larger rewards. To reduce mining fees, faucets normally save up these small individual payments in their own ledgers, which then add up to make a larger payment that is sent to a user's bitcoin address.

As bitcoin transactions are irreversible and there are many faucets, they have become targets for hackers stealing the bitcoins.