BTC is a digital currency which is used and distributed electronically. It is a decentralised peer-to-peer network, meaning no single institution or person controls it. BTC cannot be printed, and their amount is very limited – only 21 million can ever be created. It was first introduced as an open-source software by an anonymous programmer, or a group of programmers, under the alias Satoshi Nakamoto in 2009. Around mid-2010, Nakamoto moved on to other things, leaving Bitcoin in the hands of a few prominent members of the BTC community. Also, he named Gavin Andresen a lead developer. It has been estimated that Nakamoto owns around one million Bitcoins, which amounts to approximately $3.6 billion as of September 2017.