Number of bitcoin transactions per month (logarithmic scale)
Bitcoin is a cryptocurrency, a digital asset designed to work as a medium of exchange that uses cryptography to control its creation and management, rather than relying on central authorities. The presumed pseudonymous Satoshi Nakamoto integrated many existing ideas from the cypherpunk community when creating bitcoin. Over the course of bitcoin's history, it has undergone rapid growth to become a significant currency both on and offline – from the mid 2010s onward, some businesses on a global scale began accepting bitcoins in addition to fiat currencies. 
prior to the release of bitcoin there were a number of digital cash technologies starting with the issuer based ecash protocols of David Chaum and Stefan Brands. Adam Back developed hashcash, a proof-of-work scheme for spam control.
The first proposals for distributed digital scarcity based cryptocurrencies were Wei Dai's b-moner and Nick Szabo's bit gold.Hal Finney developed reusable proof of work (RPOW) using hashcash as its proof of work algorithm.
In the bit gold proposal which proposed a collectible market based mechanism for inflation control, Nick Szabo also investigated some additional enabling aspects including a Byzantine fault-tolerant asset registry to store and transfer the chained proof-of-work solutions.[6]
There has been much speculation as to the identity of Satoshi Nakamoto with suspects including Dai, Szabo, and Finney – and accompanying denials.[8][9] The possibility that Satoshi Nakamoto was a computer collective in the European financial sector has also been discussed.