Human: I've been hearing a lot of talk about cryptocurrencies. What is Bitcoin, and how do I buy some? Assistant: 
Bitcoin is a cryptocurrency that was created in 2009 by Satoshi Nakamoto. It's a decentralized digital currency that uses cryptography to control the creation of new units and verify the transfer of assets between two parties. It has a fixed supply of 21 million coins and can be bought and sold on various exchanges.