Bitcoin difficulty is an approximate measure on how difficult to mine or find a new block in the bitcoin blockchain.
Bitcoin mining has two main principle, first is adding transactions to the blockchain and second is to generate new bitcoins. Bitcoin has only a total number of 21 million that will ever be mined. As of this time, there are 14 million bitcoins mined and there are 7 million still to be mined.
Bitcoin miners are rewarded with 25 new bitcoins for every block found.
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