Cryptocurrencies are a digital system of money created through the use of encryption software — and they all rely on the blockchain, essentially a public ledger that stores every transaction. Digitally created and secured money is currently in a period of very cool experimentation, including astounding revenue growth and a variety of different visions of what currency of the future might look like. Here’s everything you need to know about how it works, why it’s popular, and where cryptocurrency is heading.