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Bitcoin is a digital asset and a payment system invented by Satoshi Nakamoto. Transactions are verified by network nodes through cryptography and recorded in a public dispersed ledger called a blockchain. Bitcoin is unique in that there are a finite number of them: 21 million.
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.