Human: I have been hearing a lot about bitcoins lately. What is a bitcoin? Assistant: 
A bitcoin is a digital currency that is not controlled by any government or central bank. It was created in 2009 by an anonymous person or group of people using the alias Satoshi Nakamoto. The name comes from the fact that each coin is made up of a fixed number of bits, and the total number of coins in circulation is capped at 21 million.