Bitcoins are created as a reward for payment processing work in which users offer their computing power to verify and record payments into a public ledger. This activity is called mining and miners are rewarded with transaction fees and newly created bitcoins. Besides being obtained by mining, bitcoins can be exchanged for other currencies, products,and services. Users can send and receive bitcoins for an optional transaction fee.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.

Bitcoin is a digital asset and a payment system invented by Satoshi Nakamoto,who published the invention in 2008 and released it as open-source software in 2009.The system is peer-to-peer; users can transact directly without an intermediary. Transactions are verified by network nodes and recorded in a public distributed ledger called the block chain.The ledger uses bitcoin as its unit of account. The system works without a central repository or single administrator, which has led the U.S. Treasury to categorize bitcoin as a decentralized virtual currency. Bitcoin is often called the first cryptocurrency, although prior systems existed.Bitcoin is more correctly described as the first decentralized digital currency.It is the largest of its kind in terms of total market value.

The unit of account of the bitcoin system is bitcoin. As of 2014, symbols used to represent bitcoin are BTC,amounts of bitcoin used as alternative units are millibitcoin (mBTC), microbitcoin (µBTC), and satoshi. Named in homage to bitcoin's creator, a satoshi is the smallest amount within bitcoin representing 0.00000001 bitcoin, one hundred millionth of a bitcoin. A millibitcoin equals to 0.001 bitcoin, which is one thousandth of bitcoin. One microbitcoin equals to 0.000001 bitcoin, which is one millionth of a bitcoin. A microbitcoin is sometimes referred to as a bit.As of February 2015, over 100,000 merchants and vendors accept bitcoin as payment.Instead of a 2–3% fee typically imposed by credit card processors, merchants accepting bitcoins often pay fees of 0% to less than 2% of the total purchase.